Process for manufacturing a filament wound, localized strength tool handle

In a process for manufacturing a handle for a hand tool, resin-coated fibers are pultruded to form an elongate, substantially hollow fiber-resin composite rod having a first end for attachment to a tool head. A glass filament is wound about a longitudinal axis of the composite rod adjacent to the rod's first end, after which an encasement over the filament is molded onto the rod. For increased strength, the filament may be first coated with a thermo-setting resin and, after wrapping the filament about the rod, the resin is cured prior to the molding step. The resultant tool handle, particularly useful in applications with, for example, lopping shears, may be very lightweight and yet exhibit superior strength characteristics in comparison with standard composite handles manufactured in a pultrusion manufacturing process. Preferably the resultant tool handle includes a substantially hollow core that extends the length of the handle, core includes a lightweight filler extending along a first portion thereof and a relatively strong reinforcing section extending along a second portion. The reinforcing section is located adjacent to the first end of the rod that is intended to withstand greater stress than the remainder of the handle.

BACKGROUND OF THE INVENTION 
This invention relates to fiber-resin composite pultrusion methods and 
products. More particularly, the present invention relates to composite 
tool handles and the like having a construction which significantly 
increases the localized strength characteristics of such handles without a 
significant corresponding increase in weight. 
In manufacturing a handle for a hand tool such as a shovel, a variety of 
competing design considerations are at stake. On the one hand, it is 
desirable to have a handle that is as light as possible, to provide for 
easy use by consumers. On the other hand, the handle must have the 
structural integrity to withstand the variety of stresses that will be 
placed on it. Wooden handles have been widely used in the past, but 
provide an often unacceptable compromise of weight versus structural 
integrity. 
An alternative to wooden handles is the use of rods formed from resin 
coated fibers. The basic technique for running filaments through a resin 
bath and then through an elongated heated die tube to produce a cured 
composite rod of the same shape as the die tube has been known for some 
time. See, for example, U.S. Pat. Nos. 2,948,649 and 3,556,888. This 
method, however, produces a solid extruded product which is unacceptably 
heavy and/or too rigid for many tool handle applications. 
The weight problem can be alleviated by means of an existing process to 
extrude hollow tubes utilizing a die tube with the center filled, leaving 
an annular cross-section through which the resin coated fibers are pulled. 
This weight reduction is achieved, however, at the cost of significantly 
reduced bending or flexural strength in comparison with a solid rod, 
resulting in a tool handle which would not be suitable for use in certain 
high-stress applications such as general purpose shovel handles. Further, 
to increase interlaminar strength of the tube forming fibers, a 
substantial percentage of fibers running other than in a longitudinal 
direction have been thought to be required. 
The bending strength of tool handles can be improved by producing 
fiber-resin rods which are substantially hollow or lightweight throughout 
a major portion of their length, but reinforced at areas of expected high 
stresses during tool use. Such improved tool handles and related methods 
are shown in U.S. Pat. No. 4,570,988, the contents of which are 
incorporated herein by reference. These composite tool handles have 
further been improved by the introduction of one or more reinforcing beads 
of fiber-resin material extending the length of the load-bearing rod. 
Such tool handles are shown in U.S. Pat. No. 4,605,254, the contents of 
which are incorporated herein by reference. 
Although such above-described composite tool handles are generally superior 
to wooden handles, the competitive pressures of the marketplace have 
encouraged tool handle manufacturers to seek new processes, materials and 
construction techniques to further increase the strength of composite tool 
handles without introducing additional weight and/or cost to the handle. 
In this regard, it is important to permit use of the most economical glass 
fibers and the most reasonably priced resins to produce a product that has 
the greatest value to the end user. However, common glass fibers and 
resins have physical properties which are often less desirable when 
utilized in a composite tool handle than other more exotic and costly 
fibers and resins. Accordingly, one objective is to obtain higher 
mechanical strength properties in a composite material tool handle while 
permitting the manufacturer to use relatively less costly fiber and resin 
materials. 
A lopping shear with, for example, twenty-two inch (22") long handles is 
about the most demanding cantilevered-type tool in popular use. Loading on 
the handles of a lopping shear is only limited by the upper body strength 
of the user. Failure in such tool handles typically occurs at or near the 
junction of a tool tang and the handle. The remainder of the handle, from 
two or three inches away from the end of the tang to the butt end seldom 
if ever fails, but must include enough mass to be comfortable to hold by a 
user. 
A study of cantilevered tool handles that have failed indicates where, why 
and what kind of strength is needed in such handles. In particular, the 
strength required of the handle diminishes in a straight-lined curve from 
the connection to the tang, to the butt end. The butt end of the handle, 
however, must be of adequate size to be comfortable to be gripped by the 
user. When wood is utilized, the handle is typically attached by slotting 
the shaft so that the metal tang of a shear can be inserted. Afterwards, 
holes are drilled through the assembly and rivets or bolts fix the 
assembly together. By slotting the wood and then drilling the holes, the 
shaft is weakened by at least the value of the cross section removed. 
Moreover, the mode of failure is almost always (unless it is a 
faulty-grained shaft of wood) in and around the attachment. Sometimes the 
metal tang breaks at the point where it had been drilled to accept the 
bolt or rivet. 
By studying test data it has become apparent that (a) bulk is required at 
the position of the handle which is to be grasped, but high-strength is 
not needed at such locations, (b) shaft strength should be at its highest 
(as required) at or around the tang attachment area, but can be 
substantially reduced progressively towards the grip, and (c) because such 
tools are often held up during use, as in the case of lopping shears, 
weight is an important consideration, and thus weight in the butt-end of 
handle is undesirable. 
Accordingly, it is desirable that an improved tool handle for use in 
connection with cantelevered-type tools be provided which is capable of 
eliminating any holes in the tang and/or handle shaft to maximize the 
strength of each component at the point of attachment between the tool 
head and the tool handle. Further, attachment must be effective without 
degrading either the tang or shaft, and/or affecting the cosmetics or 
style of the resultant tool. It is preferred that a lightweight shaft be 
provided with an ergonomic design in the grip area and which has increased 
shaft strength far superior to that available with present wood and/or 
composite tool handles. The present invention fulfills these needs and 
provides other related advantages. 
SUMMARY OF THE INVENTION 
The present invention resides in a process for manufacturing a hand tool, 
and the resultant filament wound, localized strength tool handle. Such 
tool handles are particularly useful in applications where the weight of 
the handle must be reduced to an absolute minimum while providing superior 
strength characteristics at the attachment point between the handle and 
the tool head as in, for example, lopping shears. 
In a preferred form of the invention, a pultrusion process is utilized to 
form an elongate substantially hollow fiber-resin composite rod having an 
end segment for receiving a mounting tang of a tool head. The pultrusion 
process includes the steps of alternately feeding sections of lightweight 
core and relatively strong reinforcing core into the center of the 
pultrusion die tube. The core sections are then surrounded with 
resin-coated fibers as they are pulled through the pultrusion die tube. 
Within the pultrusion die tube the resin-coated fibers are cured about the 
core sections to form a bond therewith. Preferably, the lightweight core 
comprises hollow tubing and the reinforcing core is positioned adjacent to 
the lightweight core and is at least coextensive with the rod end segment 
to increase the strength of the rod at a critical stress point. 
A glass filament is then wound perpendicularly about a longitudinal axis of 
the rod over the rod end segment. An encasement is molded onto the rod 
over the filament, and a grip is molded over an opposite end of the rod. 
For increased strength, the glass filament may first be coated with a resin 
prior to winding it about the rod. In this case, the resin is cured prior 
to the molding step. 
The resultant tool handle comprises an elongate, substantially hollow core 
having a lightweight filler extending along a first portion of the 
predetermined length and a relatively strong reinforcing section extending 
along a second portion of the length. The first and second portions extend 
alternately longitudinally along the length of the tool handle such that 
the reinforcing section of the core is located adjacent to a first end of 
the tool handle where it is intended to withstand greater stress than the 
remainder of the handle. A generally tubular jacket of fiber-resin 
material is formed about the core, and a glass filament is wound about a 
longitudinal axis of the jacket adjacent to the first end thereof. The 
filament is sealed between the jacket and an encasement molded onto the 
jacket over the filament, and a grip is provided over a second end of the 
tubular jacket. 
Other features and advantages of the present invention will become apparent 
from the following more detailed description, taken in conjunction with 
the accompanying drawings which illustrate, by way of example, the 
principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in the drawings for purposes of illustration, the present 
invention is concerned with a novel composite tool handle, generally 
designated in the accompanying drawings by the reference number 10, and a 
related manufacturing process. A pair of tool handles 10 comprise 
components of an exemplary hand tool shown in FIG. 6 as lopping shears 12. 
The exemplary lopping shears 12 include a tool head 14 defined by a pair 
of pivotally interconnected and opposed blade members 16. The blade 
members 16 are connected in turn to a corresponding pair of handles 10. In 
this regard, the blade members 16 of the tool head 14 each include a 
rearwardly projecting mounting tang 18 formed typically from a tool steel 
in integral relation with the blade members (FIG. 6.). 
In accordance with the present invention, the tool handle 10 comprises a 
load-bearing rod 20 having molded thereon a cosmetic ferrule 22 at a first 
end thereof and a grip 24 over a second end thereof. The ferrule 22 
ensheaths a portion of the rod 20 that is configured to receive a mounting 
tang 18 of the tool head 14 therein, in the manner described in U.S. Pat. 
No. 5,123,304, the contents of which are incorporated herein. 
The load-bearing rod 20 is manufactured by a pultrusion process 
(schematically illustrated in FIG. 1), and includes alternating sections 
of lightweight filler core 26 and a reinforcing core 28 surrounded by a 
cured fiber-resin jacket 30. The reinforcing core 28 is preferably located 
within the fiber-resin jacket 30 at or adjacent to the first end of the 
rod 20, where the greatest flexural stresses on the tool handle 10 are 
anticipated during normal tool use. The lightweight filler core 26, which 
may be simply hollow tubing, extends through the remainder of the 
load-bearing rod 20 to minimize the weight of the tool handle 10. 
More particularly, the load-bearing rod 20 is manufactured by drawing a 
fiber material 32 through a resin bath 34 and into a die tube 36 where the 
fibers are heated and cured by a heating element 38 surrounding the die 
tube. The cured rod is pulled out of the die tube 36 by tractor-type 
pullers 40 and cut to the desired length by a conventional cutting device 
42. As the fibers 32 enter the die tube 36, alternating sections of 
lightweight tubing or filler core 26 and reinforcing core 28 are inserted 
into the center of the die tube and are simultaneously surrounded by the 
fibers and drawn into and through the die tube 36. By this method a 
continuous load-bearing rod 20 can be quickly and easily manufactured with 
a reinforced section integrally included at any desired location, and for 
purposes of the present invention preferably at a first end thereof. 
In order to greatly improve the strength characteristics of the tool handle 
10 adjacent to the first end thereof, a glass filament 44 is run through a 
second resin bath 46 and, wound about a longitudinal axis of the rod 20 
adjacent to the rod's first end. The second resin bath 46 preferably 
includes a thermo-setting resin such as an epoxy The resin is cured prior 
to molding the ferrule 22 onto the rod 20 over the glass filament windings 
44. 
Although the glass filament 44 comprises a bundle of extremely small 
threads which are very fragile and can be easily damaged, the filament 
typically has a high tensile strength. Further, great strength values will 
be realized if the individual fibers have a resin bridge to disperse the 
load from fiber to fiber. Therefore, to give the highest values the fibers 
are first coated with a thermo-setting resin in the resin bath 46 either 
during wrapping or thereafter, and then cured. However, many applications 
do not require the ultimate possible strength and, therefore, the fibers 
can be "dry" wrapped about the rod 20 and need only a protective covering 
in the form of the ferrule 22 to be molded over the windings 44 and onto 
the rod 20. It has been found that two layers of dry glass, cheek-wrapped 
glass filament 44 windings significantly improve the strength of the tool 
handle 10 at its attachment to the tool head 14, in connection with the 
exemplary lopping shears 12. In other applications, more or less layers 
laid on in various patterns, wetted or dry, may be employed to get the 
desired strength characteristics from the tool handle 10. 
Following manufacture of the handle 10 as described above, it may be 
attached to the tool head 14 in much the same manner as described in U.S. 
Pat. No. 5,123,304. In particular, a mounting tang 18 may be first heated 
within a heating block. The first end of the tool handle 10 is then 
aligned with the heated mounting tang 18 to place an end of the 
reinforcing core 28 (and a channel provided therein) in alignment with the 
mounting tang 18. The tool handle 10 is then driven onto the mounting tang 
18 so that the mounting tang is forced into the reinforcing core 28. The 
thermo plastic material of the reinforcing core 28 surrounding the tang 18 
flows into intimate contact around the mounting tang and then hardens as 
the heat of the mounting tang is dissipated to hold it in place. Thus, no 
screws or rivets are required to join tool handle 10 to the tool head 14. 
The resultant tool handle 10 comprises an elongate, substantially hollow 
core which includes the abutting filler core 26 and reinforcing core 28. A 
generally tubular jacket 30 a fiber-resin material is cured about the 
cores, and a glass filament 44 is wound about the longitudinal axis of the 
jacket adjacent to a first end thereof. An encasement in the form of the 
ferrule 22 is then molded onto the jacket 30 over the filament 44. 
Simultaneously, a grip 24 is molded over a second end of the tubular 
jacket. The glass filament 44 may be coated with a thermo-setting resin 
and cured over the jacket 30 if additional strength is needed adjacent to 
the first end of the tool handle 10. 
From the foregoing it will be appreciated that the present invention 
provides a filament-wound, localized strength tool handle and a related 
manufacturing process. The features of the tool handle include a high 
dielectric strength, high chemical and weather resistance, infinite color 
and grip styling, and the ability to utilize heat drive assembly of the 
handle to the tang, thereby eliminating the need for bolts or rivets. The 
shelf life of such a tool handle 10 is essentially infinite, the color of 
the tool handle may be built in, thereby eliminating the need for paint or 
varnish, and the flexural modulus of the composite tool handle, in 
comparison with wood, provides superior shock absorption. Further, it 
should be understood that the process described above may be enhanced by 
combining other advanced manufacturing processes such as those shown and 
described in U.S. Pat. Nos. 5,262,113 and 5,421,931, the contents of which 
are incorporated herein. 
Although a particular embodiment of the invention has been described in 
detail for purposes of illustration, various modifications may be made 
without departing from the spirit and scope of the invention. Accordingly, 
the invention is not to be limited, except as by the appended claims.