Note: Descriptions are shown in the official language in which they were submitted.
CA 02456066 2004-01-27
ERGONOMIC TOOL HANDLE AND RELATED HAMMER
SYSTEM
FIELD OF THE INVENTION
The present invention relates to an ergonomic tool handle and more
particularly relates to a hammer system including various ergonomic features.
BACKGROUND
Most hand tools are based on designs which have been around for
decades or centuries and can in most cases benefit from improvements in their
design made using modern ergonomic and biomechanical design and measurement
techniques. Ergonomic hand tools are generally designed to minimize the effort
and
strain on the human body while maximizing their efficiency. Many diseases such
as
Carpal Tunnel Syndrome, Tendinitis, Bursitis, and Tenosynovitis can be caused
by
repeated use of poorly designed tools. It is known that hand tools should be
designed
to limit the motion of the wrist to the middle third of the range of motion to
help reduce
the risk of these diseases. Ergonomic hand tools having bent handles to
improve the
efficiency of the tool and limit the range of motion of the wrist have been
known for
some time. One example of which is the Bennett handle which provides a curved
handle grip which angles vertically downwards into the hand and follows the
line
between the index finger and the ball of the thumb. This handle when employed
for
example on a hammer reduces the range of motion of the wrist and improves the
striking angle of the hammer. The Bennett handle however does not bring the
tool into
alignment with the forearm. This requires that the individual using the tool
angle their
wrist slightly to bring the tool into alignment with the forearm during use.
This can
result in repetitive strain injuries if the tool is used often or for long
periods of time.
Most hand tools have a handle which is substantially straight. This tends to
result in
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the tool head falling in the line of sight of the individual 5 using the tool
and obscuring
the work area.
Canadian Patent 2,208,951 discloses a handle design with improved
ergonomics in view of the above prior handle designs, however the tool head is
not
suitably aligned with the offset gripping portion for all applications,
accordingly, the
applications of the handle to a hammer head are limited.
SUMMARY
According to one aspect of the present invention there is provided a
hand tool comprising:
a tool head for performing work;
a handle including a main portion extending in a longitudinal direction
between a gripping portion and a tool head supporting portion opposite the
gripping
portion;
the gripping portion being offset at an inclination in relation to the
longitudinal direction of the main portion; and
the tool head supporting portion being offset at an inclination in relation
to the longitudinal direction of the main portion.
The gripping portion and the tool head supporting portion are preferably
offset at a lateral angle from the main portion in a same direction and offset
at a
vertical angle from the main portion in opposite directions such that both the
gripping
portion and the tool head supporting portion are offset from the main portion
of the
handle at a compound angle including the lateral angle and the vertical angle.
Offsetting both the gripping portion and the tool head supporting portion
ensures that the tool head is properly aligned with the gripping portion while
improving
the line of sight to the tool head of the person using the tool handle.
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In the example of hammers, the hammer works by transferring
momentum or releasing kinetic energy during impact with a nail or other
objects. For
typical power grip hammering operations, impact time is less then a
millisecond, with
peak accelerations of several thousand meters per second squared. The
ergonomic
handle serves as an attenuator so that the vibration and referred impact shock
is not
transmitted to the user's hand, and from there elsewhere to the human body,
each
time the hammer impacts a surface.
According to a second aspect of the present invention there is provided
a hammer comprising:
an elongate handle having a main portion and an end portion of reduced
dimension;
a head having a body and an opening formed in the body for snugly
receiving the end portion of the handle therein; and
fastening means for securing the end portion of the handle within the
opening in the head whereby the head remains selectively separable from the
handle.
In the event the hammerhead and hammer handle interface are
designed as a fixed system, the threaded or other fastening means acts upon
the
hammer and handle connection as a support and stiffener rod to increase its
strength
substantially , so that the tool can also be used for prying or extracting
object's .
The opening preferably extends through the body of the head with a
wedge for being snugly received in one end of the opening and the narrow
portion of
the handle being received in an opposing end of the opening.
The wedge may include a through bore receiving the fastening means
therethrough.
There may be provided a compression plate member spanning the end
of the opening receiving the wedge therethrough with the fastening means
securing
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the plate member to the handle for clamping the head and wedge member
therebetween.
There may be provided a plurality of interchangeable wedges having
differing weights.
The fastening means may comprise a threaded rod supported on the
handle and a threaded nut securing the head between the nut and the handle.
The threaded rod is preferably received in a bore formed in the handle
with a compressible member surrounding the rod within the bore.
The fastening means may include a first threaded member secured to
the handle and a second threaded member for mating with the first threaded
member.
The fastening means may further include a resilient washer clamped between
confronting faces of the first and second threaded members.
The handle preferably includes reinforcing hafting material surrounding
the main portion adjacent the end portion supporting the head thereon.
When the body of the head extends in a longitudinal direction of the
head between an impact face which is perpendicular to the longitudinal
direction and
a claw member which curves in the longitudinal direction towards the handle
and in
which the handle is supported transversely to the longitudinal direction of
the head,
preferably there is provided a domed fulcrum member selectively mounted on the
body of the head opposite the handle. Alternatively, the domed fulcrum member
may
be integrally formed on the body of the head opposite the handle continuous in
profile
with the claw member.
The hammer may be part of a kit including a plurality of heads, each
having an opening formed therein of similar configuration for receiving the
end portion
of the handle therein and each head varying in dimensions from remaining heads
of
the kit. In this instance, at least one head may include an impact area
differing in
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dimensions from remaining heads of the kit and at least one head may include a
weight which is greater than a weight of each of the remaining heads of the
kit.
The main portion of the handle of the hammer may extend in a
longitudinal direction of the handle between a gripping portion of the handle
and the
end portion supporting the head thereon opposite the ,gripping portion. Both
the
gripping portion and the end portion in this instance are preferably offset at
an
inclination in relation to the longitudinal direction of the main portion.
The gripping portion and the tool head supporting portion of the hammer
handle are preferably offset at a lateral angle from the main portion in a
same
direction and offset at a vertical angle from the main portion in opposite
directions
such that both the gripping portion and the tool head supporting portion are
offset
from the main portion of the handle at a compound angle including the lateral
angle
and the vertical angle.
According to a further aspect of the present invention there is provided a
hammer comprising:
an elongate handle having a main portion and an end portion of reduced
dimension, the handle including an elongate bore extending from an open at the
end
portion to a terminal end within the handle;
a head having a body and an opening formed in the body for snugly
receiving the end portion of the handle therein; and
a tension member received through the bore in the handle and secured
under tension between the terminal end of the bore and the head.
The tension member preferably comprises a rigid rod threadably
secured to the terminal end of the bore at one end. When the head is secured
to the
handle by a clamping member, the opposing end of the tension member is
preferably
threadably secured to the clamping member.
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When the bore extends at least one third a length of the handle, the
handle is preferably maintained under compression between the terminal end of
the
bore and the end portion of the handle by the tension member.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate exemplary embodiments
of the present invention:
Figure 1 is a top plan view of a prior art hammer supported in a person's
hand.
Figure 2 is a top plan view of a tool in accordance with the present
invention, shown supported in a person's hand.
Figure 3 is an exploded perspective view of a hammer.
Figures 4 and 5 are respective top plan and side elevational views of the
hammer according to Figure 3 when supported in a person's hand.
Figure 6 is a sectional view of a hammer head supported on the
ergonomic tool handle.
Figures 7 and 8 are side elevational views of varying tool heads for
being supported on the handle of the present invention.
Figure 9 is a rear elevational view of a further embodiment of the tool
head.
DETAILED DESCRIPTION
Referring to the accompanying drawings, there is illustrated an
ergonomic hand tool generally indicated by reference numeral 10. The tool 10
includes an ergonomic handle 12 for supporting a tool head 14 thereon to
perform
useful work.
The handle is ergonomically shaped for gripping at an offset angle in
relation to the tool head to bring the tool head into alignment with the
forearm of the
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individual using the tool. The handle helps reduce many of the inefficiencies
associated with conventional hand tool designs and helps reduce the risk of
repetitive
strain injuries. While a hammer is illustrated as the preferred embodiment,
the tool
handle is useful and can readily be applied to paint brushes and scrappers,
sheering
tools including scissors and the like, writing instruments such as a pen or
any other
hand tool in which working or sporting goods or other equipment associated
with
implements are supported on a handle.
The handle 12 includes a main portion 16 which extends generally
straight in a longitudinal direction 18 with a smooth contoured surface. A
gripping
portion 20 is supported at one end of the main portion 16 to extend therefrom
at a
compound angle relative to the longitudinal direction of the main portion.
Opposite
the gripping portion 20, there is provided a narrowing, wedge shaped, end
portion 22
extending from the main portion 16 which includes a portion of reduced
dimension to
define a shoulder 24 against which the tool head 14 abuts when mounted on the
handle. The end portion 22 and a transition portion 26 of the handle which
connects
the end portion 22 to the main portion 16, extend at a compound angle relative
to the
longitudinal direction 18 of the main portion.
The compound angle of each of the gripping portion 20 and the narrow
end portion 22 in relation to the main portion 16 include a lateral angle and
a vertical
angle. The lateral angle is defined as a deviation from a vertical plane
locating a
longitudinal direction of a forearm of the person supporting the hand tool in
their hand
and also containing the longitudinal direction 18 of the main portion. The
vertical
angle is defined as an angular deviation from a horizontal plane containing
the
longitudinal direction 18 of the main portion of the handle and the
longitudinal
direction of the forearm of a person gripping the handle in their hand.
The vertical angle of the gripping portion is a downward angle from the
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horizontal plane while the narrow end portion 22 has an opposing upward
deviation
such that, in side elevational view, the handle follows and S-shaped profile.
The
lateral angle of both the gripping portion 20 and the end portion 22 are in
the same
direction, comprising an interior direction which the palm of a hand of the
person
gripping the tool faces such that in a top plan view the handle follows a
continuous
arcuate profile which is concave on an interior side which the palm of the
person
gripping the handle faces.
In the illustrated embodiment the tool head 14 comprises a hammer
head. The hammer head includes a body 28 which extends in a longitudinal
direction
between an impact face 30 lying perpendicular to the longitudinal direction of
the body
and a claw member 32 opposite the impact face. When the head is mounted on the
tool handle, transversely to the handle with a longitudinal direction of the
head lying
generally perpendicular to the directions which the end portion 22 extends,
the claw
member 32 extends outwardly in the longitudinal direction of the head at a
curve
inward and downward towards the handle. The claw member generally comprises
two fingers 34 having a V-shaped gap therebetween to act as a nail puller
similar to
conventional hammer designs.
The body surrounding the impact face 30 is generally cylindrical in
shape and narrows at a neck 36 forming one or more through bores 37 therein to
act
as a vibration arrester port before becoming enlarged at a main portion of the
body 28
which locates a through opening 38 therein. The through opening snugly
receives the
end portion 22 of the handle at an inner end 40 thereof while snugly receiving
a
wedge member 42 at an opposite outer end 44 of the opening. The end portion 22
is
wedge shaped so as to snugly secure the tool head thereon in a wedging action.
The wedge member 42, the end portion of the handle and the opening
38 all have a matching square cross section with the depth of the opening 38
being
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approximately double the depth of each of the end portion and the wedge such
that
the end portion and the wedge are received end to end across the full depth of
the
opening. Any other shape of cross section including various polygonal shapes,
or
round and oval shapes may be used as desired.
The wedge member 42 increases in cross sectional dimension towards
the outer end 44 of the opening within which it is received for retaining the
hammer
head on the handle when the wedge is secured to the end portion of the handle.
The
wedge member has a suitable thickness to project slightly beyond the outer end
44 of
the opening when the hammer head is coupled to the handle so as to permit some
slight compression of the wedge member within the body of the hammer head.
A recess 46 is formed in the outer end 44 about the opening so as to be
slightly larger in dimension then the opening. A compression plate 48 is
provided
which fits within the recess to span the opening 44 and cover the wedge member
42
received therein.
The end portion of the handle includes a bore 50 formed therein which
lies generally parallel to the direction which the end portion of the handle
extends.
The bore 50 extends from an open end at the end portion of the handle, at
least one
third a length of the handle, to a terminal end of the bore inside the handle.
A
mounting rod 52 is provided which has screw threads at an inner end for
anchoring
within the bore 50 in the handle at the terminal end of the bore to retain the
rod in the
handle. The bore 50 is slightly larger in diameter than the rod 52 to permit a
compressible spring 54 to be received about the rod within the bore 50.
The rod 52 has a suitable length so as to project outward from the
handle a distance which is similar or less than the thickness of the wedge
member.
The free end of the rod 52 projecting externally from the end portion of the
handle is
externally threaded for receiving a threaded nut 56 thereon. The wedge member
and
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the compression plate 48 received thereon each include respective bores 58 and
59
in alignment with the rod 52 for receiving the rod therethrough.
The nut 56 comprises a sleeve which is internally threaded and of
suitable dimension to be received within the respective bores in the plate and
wedge
member to be threaded overtop of the rod. A head of the nut is supported at
the
external end of the sleeve and includes a socket formed therein for tightening
of the
nut overtop of the external threading of the rod with which the nut mates.
A resilient rubber washer 60 is provided about the sleeve for abutting
the confronting face of the nut 56 which clamps down onto the compression
plate for
clamping the plate and wedge member with the surrounding hammer head between
the face of the nut and the shoulder of the handle with which the tool head
abuts.
When the nut is secured on the end of the rod 52, the rod which is a
rigid member, is under tension between the terminal end of the bore and the
nut 56
which acts as a clamping member securing the head to the handle. The handle
accordingly is under compression between the terminal end of the bore and the
head
for increasing the strength thereof by introducing a pre-stressed condition to
the
material forming the handle regardless of whether the handle is formed of
wood,
fibreglass, metal or other materials.
A reinforcing mesh hafting material 62 is wrapped about the transition
portion of the handle and about the shoulder defined at the end portion to
provide
added reinforcement of the handle adjacent the tool head which is mounted
thereon.
A fulcrum attachment 64 is provided which can be secured at the outer
end of the opening on top of the hammer head, opposite the handle. The fulcrum
attachment includes a domed outer surface which is convex in profile to extend
outward from the body of the hammer head opposite the handle in a curved
profile
which is continuous with the curve of the claw member. A hole 68 in the outer
surface
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receives the nut 56 to permit selective attachment with the threaded fastener
of the
tool head securement to the handle. As well, the hole 68 also facilitates
provisions for
pulling smaller nails.
As illustrated in Figure 7, in an alternate design of the hammer head, the
fulcrum attachment may be formed integrally with the body of the hammer head.
As illustrated in Figure 8, in further embodiments the body of the
hammer head may have varying dimensions to vary the size of the impact face or
to
produce a heavier hammer having greater impact. In the embodiment of Figure 8,
the
portion of the body surrounding the impact face forms a cylindrical portion
larger in
diameter than in the previous embodiments and which extends a greater depth
before
the reduced dimension of the neck leading to the main portion of the body.
As illustrated in Figure 9 an optional hammer head to be included with
the other head designs disclosed herein as a kit with the handle, may include
a claw
member in which the pair of fingers of the claw are inclined in a generally V-
shaped
configuration in cross section for a greater accessibility in corners between
a floor and
wall for example as illustrated. Details of the angled claw member are
disclosed in
Canadian patent 2,208,951.
As described above, an ergonomic tool handle is provided which can
readily be applied to various hand tools. In the illustrated embodiment a
plurality of
different hammer heads may be provided which are selectively mounted using
threaded fasteners onto the handle to permit replacement of the head with
different
styles of hammer heads having different properties as required for different
applications. In some instances the wedge member alone may be desired to be
replaced to provide a wedge member of varying material density from remaining
wedge members in a kit whereby the impact force of the hammer may be varied
due
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to the varying weight at the head.
The hafting material disclosed above comprises wire mesh in the
illustrated embodiment, however the material may consist of single wire
strands which
are wrapped about the handle in single or multiple layers. Also the material
could
consist of a solid material, for example tin or composites and the like. The
hafting
provides additional support particularly when applying lateral forces for
pulling nails
and the like and is useful to prevent chipping of the handle in areas of high
risk of
failure. The hafting further provides stability and prevents splintering when
compression forces are applied as the hammer head is attached to the handle
with
the compression plate and compression nut in order to maintain a solid hammer
head
and handle interface. Stability and splintering is also provided when
compression
forces are applied when the hammer is used as a lever during extracting or
prying of
nails and other objects.
Despite the ancient and modern art of hammer design which attempted
to provide features and modern conveniences that would increase safe work
efficiency, none provide the features of the tool handle and hammer system
described
herein.
Generally, a tool or implement is comprised of two main parts, the
handle and the attachment that does the work. The concept and principle of the
tool
handle design can be applied to a multitude of other implements in addition to
the
hammer system illustrated herein, for example, in sporting equipment such as
ice
climbing picks, other construction or garden tools, and the like.
The hammer described herein is made up of two main parts, namely the
hammer handle and the hammer head. This tool features unique detachable hammer
heads along with a tool handle that allows the user to manipulate the tool
efficiently
and safely.
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The ergonomic handle design controls deviated wrist postures and
enhances visual control of the tool surface interface. The design is intended
to
maximize operator efficiency and at the same time reduce overuse injuries and
awkward postures in the wrist, arm and shoulder.
The handle features three major design qualities which adjust the tool to
adapt to the anatomical line of the wrist and forearm, improve the sight line
to the
impact surface, and increase friction to achieve a firm grip.
The medial curve causes a lateral rotation impact torque but this is
compensated for at the neck of the hammer head by a countering compound angle
including a lateral and a vertical component. The effect of this compound
angle
provides significant improved visual alignment and sight line to the target
plus
improved alignment of the handle with the forearm.
The ergonomic tool handle grip surface is designed to accommodate a
larger than usual friction surface for the power grip, and bulges and
associated anchor
points within the handle to provide palm support. The power grip involves more
of the
medial or under side of the hand and provides greater palm surface and a
firmer grip.
The precision grip involves more of the lateral aspects of the palm
including the index finger and the thumb and results in lower grip strength,
but more
control. The tool handle disclosed herein facilitates both power and precision
grip.
The purpose of the handle is to facilitate the transmission of force from the
user to the
target.
The handle design will avoid unsuitable postures and unnecessary
muscle exertion and allow the user to hold the handle securely with
appropriate wrist,
arm and shoulder posture. The bulges and anchor points along the handle allow
many
hand positions without causing compression of soft tissues, abrasions,
blisters or
formation of calluses. The bulges also provide much needed friction.
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This design calibrates the relation between handle size and hand size
which is important. If the handle is too small, not much force can be exerted,
and
large local tissue pressure might be generated. If the handle is too large for
the hand,
hand muscle must work at disadvantaged lever arms. As a result, fatigue
factors and
less grip strength come into play.
While various embodiments of the present invention have been
described in the foregoing, it is to be understood that other embodiments are
possible
within the scope of the invention. The invention is to be considered limited
solely by
the scope of the appended Claims.
