Note: Descriptions are shown in the official language in which they were submitted.
~L241502
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates generally to fastener
driving tools, and particularly to driving tools that
utilize an energy storing flywheel that selectively
engages a ram in order to drive the ram into engagement
with a fastener such as a nail or a staple in order
to drive the fastener into the workpiece.
Description Of The Prior Art
Several fastener driving tools that utilize
an energy storing flywheel for the purpose of storing
energy to drive the fastener into the workpiece are
known. Examples of representative prior art devices
are disclosed in United States Patents Nos. 4,042,036;
4,121,745; 4,129,240; 4,189,080; 4,298,072; 4,290,493
and 4,323,127. While the devices disclosed in the
above references are capable of driving fasteners
such as nails or staples into a workpiece, they do
suffer from several disadvantages, including excessive
! 20 weight and less than optimum balance. These disadvan-
tages present a particular problem in devices that
employ more than one flywheel, especially those devices
that utilize a separate motor to drive each of the
two flywheels. In addition, the prior art devices
utilize a high friction material such as brake lining
or similar material that is disposed on the surface
of the ram or on the periphery of the flywheel.
Unfortunately, such material is subject to wear because
of the high relative speed between the surface of the
~.2~150Z:
-2- 3076-998F
flywheel and the surface of the ram that is present when engagement
occurs. Also, the high pressure exerted on the brake material causes
the material to crumble prematurely. As a result, the ram or the
flywheel must be frequently replaced. Also, in the prior art dev-
ices, neither the ram nor the flywheel is readily accessible, and
consequently the replacement of these components tends to be time
consuming and costly. Finally, the prior art devices utilize a
resilient member for returning the ram to a rest position, and in
the prior art devices, the resilient member tends to fatigue and
fail after a moderate numher of fasteners have been driven.
The invention provides a tool for driving fasteners having
a housing, a ram mounted for reciprocation between an upper and a
lower position and a flywheel selectively engaging said ram to drive
said ram from said upper position to said lower position, character-
ized by: means for supporting said ram within said housing, said
supporting means including an upper resilient bumper for limiting
the upward travel of said ram and a lower resilient bumper for limit-
ing the downward travel of said ram, and vertical supports inter-
connecting said upper and lower resilient bumpers, said support means
further including an elongated elastic member resiliently supporting
saId ram in said upper position coupled to said ram, wherein said
supporting means, said ram and said elastic member are insertable
into and removable from said housing as a unit.
~241~i02
-3- 3076-998F
A further aspect of the invention consists of a fastener
driving tool having an energy storing flywheel, means coupled to said
flywheel for effecting rotation thereof, a ram and means for bring-
ing said flywheel into engagement with said ram, wherein said ram
is movable between an upper rest portion and a lower fastener en-
gaging portion, the improvement wherein said ram has an elongated
body portion having a fastener driving end and a flywheel engaging
surface, said ram further having a pair of integrally formed mem-
bers extending laterally from said elongated body portion and a
stop member supported by said laterally extending members.
DESCRIPTION OF THE DRAWING
These and other aspects of the present invention will be-
come apparent upon consideration of the following detailed descrip-
tion and attached drawing wherein:
FIGURE 1 is a left side elevation of the fastener driving
tool according to the inyention;
FIGURE 2 is a front elevation of the fastener driving tool
according to the invention;
FIGURE 3 is a cross-sectional view taken along line 3-3
20 of FIGURE 2;
FIGURE 4 is a cross-sectional view taken along line 4-4
of FIGURE l;
FIGURE 5 is a cross-sectional view taken along line 5-5
of FIGURE 1 showing the mounting of the flywheel drive motor;
; FI5URE 6 is a cross-sectional view similar to FIGURE 3
showing the drive ram in its lowermost position;
FIGURE 7 is a cross-sectional view taken along line 7-7
of FIGURE 3 showing the top of the ram supporting structure;
15C~2
--4--
FIGURE 8 is a cross-secti.onal view taken along line 8-8
of FIGURE 3 showing the construction of the ram supporting
structure;
FIGURE 9 iS a cross-sectional view taken along line 9-9
of FIGURE 6 showing the flywheel and idler wheel mechanism;
FIGURE 10 is an exploded perspective view showing the
ram supporting assembly;
FIGURE 11 is an exploded perspective view showing the
ram supporting assembly in greater detail;
I,
-5- ~24~502
FIG. 12 is a partial cross-sectional view
showing an alternative mounting of the elastic member
within the fastener driver housing;
FIG. 13 is a partial cross-sectional view
of the handle of a fastener driving tool utillzing a
battery power source;
FIG. 14 ls a left side elevational view of
another embodiment of the fastener driving tool according
to the lnvention;
FIG. 15 is a front elevatlonal view of the
fastener driving tool illustrated in FIG. 14;
FIG. 16 is a cross sectional view taken
along line 16-16 of FIG. 15;
FIG. 17 is a cross sectional view taken
along line 17-17 of FIG. 14;
FIG. 18 is a sectional view taken along
line 18-18 of FIG. 16 showing the top of the ramp
supporting structure;
FIG. 19 is a cross sectional view taken
along line 19-19 of FIG. 16;
FIG. 20 is a sectional view taken along
line 20-20 of FIG. 16;
FIG. 21 is a sectional view taken along
line 21-21 of FIG. 16 illustrating the toggle assembly
in greater detail;
FIG. 22 is a perspective view of the eccen-
tric spacer of the toggle assembly;
FIG. 23 is a sectional view taken along
- line 23-23 of FIG. 14 illustrating the canted motor
assembly;
FIG. 24 is a sectional view taken along
line 24-24 of FIG. 16;
FIG. 25 is an exploded perspective view
illustrating the upper portion of the ram housing;
2~1502
--6--
FIG. 26 is a detailed view of tne upper
portion of the ram assembly;
FIG. 27 is a perspective view, partially in
cross section, of the flywheel assembly illustrating
the resilient hub of the flywheel; and
FIGS. 28-31 are schematic diagrams of various
electrical circuits suitable for controlling the opera-
tion of the solenoid and flywheel driving motor.
DETAILED DESCRIPTION OF THE PREFERRED E~IBODIMENT
Referring now to the drawing, with particular
attention to FIG. 1, there is shown a fastener driving
tool according to the present invention generally
designated by the reference numeral 10. The Lastener
driving tool illustrated in FIG. 1 includes a housing
12 which has a vertical portion 14 and a horizontal
portion 16. A handle 18 is affixed to the housing
12, as is a magazine 20 which contains the fasteners
to be driven. In the illustrated embodiment, the
magazine 20 is designed to hold U-shaped staples, but
other suitable magazines, such as those designer to
hold nails or other fasteners, may be used with appro-
priate modifications to the fastener driving tool.
The fastener driving tool also includes a
nosepiece 22, an electric motor 24, which may powerea
either from an AC mains source or a battery power
source, an energy storing flywheel 26 (best shown in
FIG. 3) and an idler wheel 28. A safety yoke 23,
whose function will be described in a subsequent por-
- tion of the specification, is disposed within and
adjacent the nosepiece 22. A drive belt 30 inter-
connects a pulley 32, affixed to a shaft 34 of the
motor 24, and a second pulley 36, affixed to a shaft
38 of the flywheel 26, and serves to rotate the fly-
wheel 26 whenever the motor 24 is energized.
15(~;~
--7--
The shaft 38 of the flywheel 26 is supported
within the housing 12 by a pair of bearings 40 and 42
(FIG. 9) which may be ball bearings, needle bearings
or other suitable bearings. A fastener driving member
or ram 44 is supported within the housing 12 by a
subassembly 46 (FIGS. 3, 4 and 10) located within the
upper housing 14. The subassembly 46 includes an
upper travel limiting bumper 48 and a lower travel
limiting bumper 50 that serve to limit the upward and
downward travel, respectively, of the ram 44. An
elastic member, preferably an elastic shock cord 52,
sometimes known as a Bungee cord, is fabricated from
a plurality of elastic fibers bundled together, and
serves to bias the ram 44 in its uppermost position.
The idler wheel 28 is supported within two
slots 54 and 56 (FIGS. 3 and 9) of the housing 12 by
a shaft 58. A bearing 60, which may be a needle bear-
ing or a sleeve bearing fabricated from bronze or
other suitable material, permits the idler wheel 28
to rotate freely about the shaft 58. The idler wheel
shaft 58 is moved laterally within the slots 54 and
56 by a toggle mechanism 62 (FIGS. 1, 3, 8 and 9)
that includes a pair of arms 64 and 66 that support
the shaft 58, and a pair of shorter arms 68 and 70
that are pivotably mounted about the axis of the shaEt
38. The arms 64 and 68 are connected together at one
end by a screw 72, anà the arms 66 and 70 are connected
together by a similar screw 74. A spacer 76 receives
- the screws 72 and 74, and serves to maintain the arms
64, 66, 68 and 70 in a spaced parallel relationship
about the flywheel 26, and as will be explained in a
subsequent portion of the specification, also serves
to adjust the contact pressure between the flywheel
26 and the ram 44.
~L~41~02
8--
A linkage employing a pair of lever arms 78
and 80 and a Unshaped member 81 (FIGS. 1 and 3) couples
the safety yoke 23 to the toggle mechanism 62 at oppo-
site ends of the spacer 76, and causes the toggle
mechanism 62 to be toggled from the position shown in
FIGS. 1 and 3 to the position shown in FIG. 6 when
the nosepiece 22 and the safety yoke 23 are brought
into contact with a workpiece. A resilient member,
such as, for example, a spring 82, returns th2 toggle
62 to the position shown in FIGS. 1 and 3 when the
tool is disengaged from the workpiece.
A solenoid 8~ is mounted within the vertical
housing 14 and actuates a lever 86 via a solenoid
armature~88. A reduced width end 90 of the lever 86
is retained in a slot 89 of the vertical portion 14
of the housing 12. A U-shaped notch 91 at the other
end of the lever 86 engages a groove 92 in the solenoid
armature 88. A cap 94 is interposed between the lever
86 and the upper part of the ram 44 in order to mechani-
cally couple the lever 86 to the ram 44 so that energi-
zation of the solenoid 84, which causes the armature
88 to retract into the solenoid 8~, will cause the
ram 44 to be pushed down by the cap g4.
A pair of switches 96 and 98 controls the
operation of the solenoid. The switch 96 is controlled
by a manually actuated trigger or push button 100,
while the switch 98 is controlled by the safety yoke
23 via the levers 78 and 80, a U-shaped member 81 and
a wiIe link 102. The wire link 102 has one end coupled
to the spacer 76 and another end 101 disposed adjacent
the switch 98, and serves to depress a button 99 on
the switch 98 when the safety yoke 23 is brought into
contact with a workpiece. The switches are wired 50
that the solenoid 84 may be energized on]y if the
push button 100 is depressed, and the safety yoke 23
is depressed by the workpiece.
i5~2
g
In operation, the flywheel 26 is rotated by
the motor 24 in a direction to force the ram 44 down-
wardly when it is engaged by the flywheel 26. The
motor may be energized either by depressing the push
button 100, or by turning on a separate on-off switch
(not shown) which may be located at any convenient
location on the housing 12 or handle 18. In the pre-
ferred embodiment, the flywheel 26, the idler wheel
28 and the ram 44 are fabricated from metal, preferably
steel, to give a metal-on-metal, preferably steel-on-
steel, contact between the ram 44, the flywheel 26
and the idler wheel 28. A steel particularly suit-
able for the flywheel 26 is high carbon, chrome steel,
such as type D-2 or 52100 tool steel.
It has been found that for steel-on-steel
contact, in the present embodiment, the optimum speed
of rotation of the wheel 26 is that rotational speed
which results in a tangential velocity of approximately
120 feet per second at the periphery of the wheel 26.
The tangential velocity of 120 feet per second has
been selected as a suitable compromise between the
amount of energy that can be stored in the flywheel
26 and the durability of the flywheel 26 and ram 44.
Because the amount of energy that can be stored in
2S the flywheel 26 is a function of its mass and the
square of its speed of rotation, it is desirable to
make the speed of rotation as high as possible in
order to minimize the size and weight of the flywheel
26 required to drive a certain size fastener. However,
above a tangential velocity of 120 feet per second,
the surface of the flywheel 26 tends to slip when it
engages the ram 44, thus causing frictional heating
and burning at the point of contact, particularly at
the surface of the ram 44. Such burning reduces the
life of the ram 44 and eventually damages the peri-
pheral surface of the flywheel 26.
~41502
--10--
Accordingly, in the present device, the
tangential velocity of the periphery of the flywheel
26 is limited to approximately 120 feet per second.
In the present embodiment, the diameter of the fly-
wheel 26 is approximately 2.7 inches, and in order to
achieve the speed of 120 Eeet per second at the peri-
phery of the flywheel 26, the flywheel 26 is rotated
at approximately 10,500 rpm.
When the safety yoke 23 is not in contact
with a workpiece, the toggle is positioned as is shown
in FIG. 3 to maintain the flywheel 26 and the idler
wheel 28 in a spaced apart relationship, with the
spacing between the flywheel 26 and the idler wheel
28 being greater than the thickness of the ram 44.
Consequently, in this condition, no energy can be
imparted to the ram 44, even when the flywheel 26 is
rotating. When the nosepiece 22 is brought into con-
tact with a workpiece, the safety yoke 23 is raised,
and the member 81 moves downwardly from the position
shown in FIG. 3 to the position shown in FIG. 6 to
pivot the arms 68 and 70 in a clockwise direction
about the shaft 38. This, in turn, moves the arms 64
and 66 downwardly and to the right to the position
shown in FIG. 6, thereby moving the idler 28 closer
to the flywheel 26. However, because the lower portion
of the ram 44 is of reduced thickness, the flywheel
26 does not engage the ram 44 as long as the ram 44
is in its uppermost position.
Engagement only occurs after the solenoid
84 has been energized to push the ram 44 down enough
to position the thicker portion of the ram 44 between
the flywheel 26 and the idler wheel 28. This energiza-
tion of the solenoid 84 results only when the push
button 100 closes the switch 96, and the switch 98 is
closed by the rod 102 when the safety yoke 23 is brought
~L~4~50~
--11--
into contact with a workpiece as is shown in FIG. 6.
When this occurs, the ram 44 is driven downward and
into engagement with a fastener 104 within the magazine
20, and drives the fastener into the workpiece. When
driving the fastener 104, the ram 44 is driven downward
until it reaches its lowermost position, at which
position a reduced thickness section 106 is interposed
between the flywheel 26 and the idler wheel 28 (FIG.
6). This causes a temporary disengagement of the ram
44 and the flywheel 26, and prevents friction damage
to the surface of the flywheel 26 or to the ram 44
when the ram 44 is in its downwardmost position prior-
to the disengagement of the workpiece by the nasepiece
22 and safety yoke 23. In practice, the position
illustrated in FIG. 6 is only an instantaneous position
because the impact that occurs when the fastener 104
is driven into the workpiece causes the fastener driving
tool to be kicked upward. When this occurs the nose-
piece 22 and safety yoke 23 are disengaged from the
workpiece, and the toggle mechanism 62 returns to the
position illustrated in FIG. 3, thereby again increas-
ing the spacing between the flywheel 26 and the idler
wheel 28 to a value greater than the thickness of the
ram 44.
In order to compensate for manufacturing
tolerances, to assure that optimum pressure is applied
to the ram 44 during engagement by the flywheel 26 so
that excessive slippage does not occur, and to compen-
sate for wear of the ram 44 and the flywheel 26, the
toggle mechanism is provided with a mechanism for
readily adjusting the spacing between the flywheel 26
and the idler wheel 28. The adjusting mechanism can
be adjusted in the factory to compensate for variations
occurring in the manufacturing process and also in
I: 35 the field to compensate for wear, and includes a pair
~L2~1502
-12-
of eccentric end portions 103 and 105 (FIG. 9) disposed
at opposite ends of the spacer 76. Alternatively,
the end portions 103 and 105 can be made concentric
with the axis of the spacer 76, and the portions 103a
and 105a of the spacer 76 engaging the arms 64 and 66
made eccentric. Such a system is described in a sub
sequent portion of the specification describing an
alternative embodiment of the tool according to the
invention. The eccentric end portions 103 and 105
engage the shorter arms 68 and 70, respectively, and
serve to move the longer arms 64 and 66 with respect
to the shorter arms 68 and 70, and consequently, the
idler wheel 28 with respect to the flywheel 26, as
the spacer 76 is rotated about its axis. A series of
flats 107 are formed on the central portion of the
spacer 76 to permit the spacer 76 to be rotated by a
wrench or other similar tool. To adjust the spacing
between the flywheel 26 and the idler wheel 28, the
portion of the armature 88 extending from the housing
may be manually depressed to bring the thicker portion
of the ram 44 between the flywheel 26 and the idler
wheel 28, and the spacer 76 rotated until the ram 44
is gripped firmly between the flywheel 26 and idler
wheel 28. A pair of set screws 108 and 109 are pro-
vided to prevent the spacer 76 from rotating after
the desired spacing between the flywheel 26 and the
idler wheel 28 has been achieved.
The ram 44 is supported between the upper
bumper 48 and the lower bumper 50 by the elastic shock
cord 52 which passes over four pulleys 110, 112, 114
and 116 (FIGS. 3 and 6), and through the ram 44 and
through a lateral crosspiece or travel limiting stop
member 118 secured near the top of the ram 44 by a
hollow eyelet 117. The shock cord 52 causes the ram
44 to be returned from the position shown in FIG. 6
~15~)~
-13-
to the position shown in FIG. 3 when the toggle i9
toggled to the spaced apart position shown in FIG. 3.
When the ram 44 is engaged by the flywheel
26, the ram 44 is accelerated very rapidly, and the
transition from the position shown in FIG. 3 to the
position shown in FIG. 6 is almost instantaneous, for
example, on the order of approximately 0.005 to 0.01
seconds. Such rapid acceleration puts a severe strain
on any resilient device that is utilized to return
the ram to its upward position. For this reason, and
in accordance with another important aspect of the
present invention, the elastic shock cord 52 is made
relatively long to minimize the amount of stretch
that occurs along any given section of the shock cord
52.
By passing the shock cord 52 over the four
pulleys 110, 112, 114 and 116, the length of the shock
cord in its unstretched condition is approximately
four times the length of travel of the ram 44, and as
a result, the shock cord 52 is lengthened only by
approximately 50% of its original length when the ram
44 is moved from its uppermost position to its lower-
most position. This results in a substantial increase
in the life of the shock cord when compared to prior
art systems that require the resilient device to be
stretched 100% or more. Moreover, the use of a light
weight all metal ram as the ram 44 permits the ram 44
to be rapidly accelerated and easily stopped by the
bumpers 48 and 50 at the limits of travel.
In accordance with another important aspect
of the present invention, the ram 44 and its supporting
structure 46, including the upper and lower bumpers
48 and 50, respectively, the shock cord 52 and the
pulleys 110, 112, 114 and 116 are conveniently fabri-
cated as a single unit. The supporting structure 46
~24150~
-14-
is positioned within the upper portion 14 of the hous-
ing 12 by three walls of the upper portion 14, the
solenoid 84 and a wall 119, and is readily removable
from the vertical portion 14 of the housing 12. As
is best illustrated in FIGS. 10 and 11, the upper and
lower bumpers 48 and 50 are each fabricated as two
halves 48a, 48b and 50a, 50b, respectively. The bumpers
48 and 50 are separated by a pair of U-shaped vertical
support members 120 and 122. The vertical support
members 120 and 122 contain the four pulleys 110,
112, 114 and 116 which are supported by four shafts
124, 126, 128 and 130, each of which protrudes beyond
the vertical support members 120 and 122. The pro-
truding sections of the shafts 124, 126, 128 and 130
serve as convenient supports for the upper and lower
bumper halves 48a, 48b and 50a, 50b which contain
apertures to receive the shafts 124, 126, 128 and
130. The shafts 124, 126, 128 and 130 are retained
- in the apertures of the bumper halves 48a, 48b, 50a
and 50b by a press fit. The ends of the elastic shock
cord 52 are supported, for example, by a pair of bi-
furcated supports 132 and 134 located at the tops of
the vertical support members 120 and 122, respectively.
As can be seen from FIGS. 10 and 11; the
ram 44, the bumpers 48 and 50 and the elastic shock
cord together with the pulleys 110, 112, 114 and 116
and the vertical support members 120 and 122 form a
self-contained assembly 46 that can readily be inserted
into and removed from the vertical portion 14 of the
housing 12. This is an important feature because the
ram 44, the bumpers 48 and 50 and the shock cord 52
are the components that are most susceptible to wear
in a flywheel type fastener d.iving tool. Thus, the
removability of the assembly 46 allows ready replace-
ment of the most wear-prone components in the field
50;~
-15-
without the need for substantially disassembling the
device. Moreover, the simple construction of the
assembly 46, which uses four identical bumper sections,
four identical pulleys, four identical shafts and two
identical vertical support members permits ready re-
placement of the ram 44, shock cord 52 and any other
worn components without the need for stocking a large
number of different replacement parts. As a result,
the assembly 46 can readily be repaired or remanufac-
tured with a minimum of effort, either in the field
or at a repair station.
In addition, the illustrated structure 'pro-
vides a way conveniently to adjust the tension of the
shock cord 52. The ends 138 and 140 of the elastic
shock cord are exposed by removing a cover 136, which
also releases the reduced width end 90 of the lever
86 that is retainea within the notch 81 by a protrusion
137 of the cover 136. By simply stretching one of
- the ends, and repositioning one of the knots such as
a knot 142 at the end of the shock cord 52, the tension
of the shock cord 52 can be adjusted to compensate
for wear or to adjust the tension for different appli-
cations. In an alternative embodiment (FIG. 12), the
elastic shock cord 52 may be passed through a wall of
the vertical portion 14 of the housing, and the knot
142 positioned outside of the housing to permit the
tension of the shock cord 52 to be adjusted without
removing the top cap 136. The positioning of the
knot 142 outside of the housing 14 need not affect
the removability of the assembly 46 as a unit, since
the knot 142 can be readily unfastened, or alterna-
tiyely, the cord 52 can be supported in a slot in the
vertical portion 14 of the housing and retained in
position by the cap 136. In such an instance, removal
of the cap 136 will expose the top of the sloc and
~2~502
16-
permit ready disengagement of the shock cord 52 from
the wall of the housing 12.
Since the energy required to drive a fastener
into a workpiece is stored within the flywheel 26,
the size and peak power capability of the motor 24 is
relatively unimportant. Because the energy is stored
within the flywheel 26, the use of a smaller motor
will not affect the size of the fastener that can be
driven into the workpiece, but will simply affect the
rate at which the fasteners can be driven. This is
because when a smaller motor is used, it will simply
take more time for the flywheel 26 to be driven to a
speed sufficient to drive the fastener, but once that
speed is attained, the energy stored within the fly-
wheel 26 will be the same as if a larger motor hadbeen used.
The lack of a nigh peak power requirement
even permits a battery-powered motor to be used as
the motor 24. For example, it has been found that by
using a portable battery, such as a battery 144 (FIG.
13), and mounting the battery in the handle 18, a
completely portable tool can be provided.
Mounting the motor 24 (and battery 144,
when used) near the rear of the tool serves to balance
the weight of the flywheel 26 mounted- near the front
of the tool, and results in a well-balanced tool. In
addition, the use of the relatively long belt 30 pro-
vides a degree of resiliency in the power coupling
between the motor 24 and the flywheel 26, and results
in a decrease in the shock appliea to the motor 24
when the ram 44 is engaged by the flywheel 26. Such
a resilient transmission reduces the slow down of the
shaft of the motor 24 when the ram 44 en9ages the
flywheel 26.
~2~1502
--17--
Referring now to FIG. 14, there is shown
another embodiment of the fastener driving tool accord-
ing to the invention. The features of the embodiment
illustrated in FIG. 14 are similar to those of the
embodiments illustrated in FIG. 1, and consequently,
the various components of the embodiment illustrated
in FIG. 14 will be assigned reference numerals that
are 200 higher than corresponding components in the
embodiment of FIG. 1.
The fastener driving tool illustrated in
FIG. 14 includes a housing 212 which has a handle
218, a forward vertical portion 214 disposed at one
end of the axis of elongation of the handle 218, and
a rearward vertical portion 219 disposed at the other
end of the axis of elongation of the hanàle 2i8. In
the embodiment illustrated, the housing 212 may be
conveniently fabricated in two halves 212a and 212b
(FIG. 15), and one half of the forward vertical portion
214 as well as one half of the rearward vertical portion
219 is formed integrally with each of the halves 212a
and 212b of the housing 212. The housing 212 Jay be
fabricated from any suitable lightweight, high strength
material, and it has been found that a high impact
plastic is suitable for this purpose. A magazine 220
similar to the magazine 20 is affixed to the housing
212 and is provided with a nosepiece 222. An electric
motor 224, similar to the motor 22 is attached to the
rearward vertical portion 219 of the housing 212 below
the axis of elongation of the handle 218. An energy
storing flywheel 226 (best shown in FIG. 16) and an
idler wheel 228 which cooperate with an impact element,
or ram 244 to provide an impact means, are mounted
within the forward vertical portion 214 of the housing
212 on the same side of the axis of elongation of the
handle 218 as is the motor 224. Such mounting of the
~L~4150Z
-18-
motor 224 and the flywheel 226 at opposite ends of
the axis of elongation of the handle 218, and below
the axis, results in a well-balanced tool. A safety
yoke 223 is dispose within and adjacent the nosepiece
222. A pulley 232 is affixed to a shaft 234 of the
motor 224, and a second pulley 236 is affixed to a
shaft 238 of the flywheel 236. A drive belt 230 inter-
connects the pulleys 232 and 236 and serves to rotate
the flywheel 226 whenever the motor 224 is energized.
In accordance with another important aspect
of the present invention, counterrotating rotor means,
are provided to at least partially reduce the
precessional forces generated by the rotating flywheel
226. In the illustratea embodiment, the armature and
shaft 234 of the motor 224 rotate in a direction opposite
the direction of rotation of the flywheel 226 and
serve as the counterrotating rotor means. Thus, the
counterrotating mass of the armature of the motor 224
tends to cancel the precessional forces generated by
the rotating flywheel 226.
Although various drive mechanisms, such as,
for example, gears or friction coupled drive wheels,
are suitable for producing counterrotation, it has
been found that counterrotation can be simply and
effectively produced by simply connecting the belt
230 between the pulleys 232 and 236 in a figure-eight
pattern as is illustrated in FIG. 14. In order to
prevent the oppositely traveling portions of the belt
230 from interfering with each other, the axis of the
motor 224 is tilted with respect to the axis of the
flywheel 226 (best shown in FIGS. 15 and 23) to main-
tain the oppositely traveling portions of the belt
230 in a spaced relationship from each other.
The shaft 23~ and the flywheel 236 are sup-
ported within the housing 212 by a pair of bearings
~24~50~
--19--
240 and 242 (FIG. 20) which may be similar to the
bearings 40 and 42 (FIG. 9). A fastener driving member
or ram 244 is supported within the housing 212 by a
subassembly 246 (FIGS. 16 and 25) similar to the sub-
assembly 46. The subassembly 246 includes upper andlower bumpers 248 and 250, respectively, and an elastic
shaft cord 252 is utilized to bias the ram 244 in its
uppermost position.
As in the case of the previously described
embodiment, the idler wheel 228 is supported within
two slots 254 and 256 (FIGS. 15, 16 and 17) of the
housing 212 by a shaft 258. A bearing 260, similar
to the bearing 60, permits the idler wheel 228 to
rotate about the shaft 258. The idler wheel shaft
258 is moved laterally within the slots 254 and 256
by a toggle mechanism 262 (FIGS. 14, 16, 20 and 21),
similar to the toggle mechanism 62. The toggle mechan-
ism 262 includes a pair of arms 264 and 266 that sup-
port the shaft 25~, and a pair of shorter arms 26~
and 270 that are pivotably mounted about the axis of
the shaft 238. The arms 264 and 268 are connected
together- at one end by a screw 272, and the arms 266
and 270 are connected together by a screw 274. A
spacer 276 receives the screws 272 and 274, and as in
the case of the spacer 76, serves to adjust the contact
pressure between the flywheel 226 and the ram 244.
The structure and operation of the adjustment providing
spacer 276 is somewhat different than that of the
spacer 76, and will be explained in greater detail in
a subsequent portion of the specification.
A linkage employing a pair of lever arms
278 and 280 and a U-shaped member 281 (FIGS. 14 and
16) couples the safety yoke 223 to a toggle mechanism
262, and causes the toggle mechanism 262 to be toggled
from an open position wherein the ram 244 cannot be
iL2~1502
-20-
engaged to a closed or ram-engaging position when the
nosepiece 222 and safety yoke 223 are brought into
contact with the workpiece. A spring 282 returns the
toggle mechanism to its open position when the tool
is disengaged from the workpiece. thus, the toggle
mechanism 262 operates in a similar manner as the
toggle mechanism 62 (FIGS. 3 and 6).
A solenoid 284 is mounted within the vertical
housing 214 and actuates a lever 286 via a solenoid
armature 288, and forces the ram 244 down when the
solenoid 284 is energized in a manner similar to the
operation of the solenoid 84 in the previously-
discussed embodiment. The lever 286 has a reduced
width end 290 that is retained in a slot 289 of the
vertical portion 14 of the housing, and a U-shaped
notch 291 engages a groove 292 in the solenoid armature
288. A cap 294 mechanically couples the lever 286 to
the ram 244. A top cap 336 covers the solenoid assembly
and retains the reduced width portion 290 of the lever
286 within 'che notch 289 by means of a protrusion
337.
A pair of switches 296 and 298 controls the
operation of the solenoid 284 with the switch 296
being controlled by a manual push button 300 and the
switch 298 being controlled by the safety yoke 223
via the levers 278, 280 and 281 and a wire link 302.
In this manner, the operation of the switches 296 and
298 is similar to the operation of the switches 96
and 98 previously described.
The operation of the embodiment illustrated
in FIGS. 14-27 is similar to the embodiment illustrated
in FIGS. 1-13; however, there are some differences
worth~noting. These differences include differences
in the adjustment mechanism of the toggle mechanism,
differences in the construction of the flywheel, and
~L2~1~02
-21-
as previously mentioned, the counterrotation of the
motor and the flywheel to reduce precessionary forces.
With respect to the differences in the toggle
mechanisms, the toggle mechanism 262 is somewhat simpler
than the toggle mechanism 62. In the toggle mechanism
262 (best illustrated in FIGS. 19 and 20) the adjust-
ment of the spacing between the flywheel 226 and the
idler 228 is also provided by rotating the spacer
276. However, the construction of the spacer 276
(FIG. 22) is somewhat different than the construction
of the spacer 76. Firstly, rather than having a series
of flats to permit rotation of the spacer, the spacer
276 has a hole 307 drilled through the body of the
spacer 276 at right angles to the longitudinal axis
of the spacer 276. The hole 307 permits the spacer
276 to be conveniently rotated by inserting a suitable
tool such as an ice pick, a scribe, nail or any suitable
elongated object into the hole 307 to rotate the spacer
276. In addition, a series of indices 400 are disposed
on the spacer 276, and various ones of the indices
400 become aligned with a guide mark 402 disposed on
the arm 266 to provide an indication of the adjustment
of the spacing between the flywheel 226 and the idler
wheel 228. In addition, a plus sign 404 and a minus
sign 406 to indicate the appropriate direction of
rotation necessary to either increase or decrease the
spacing between the flywheel 226 and the idler wheel
228.
Another difference between the spacer 276
and the spacer 76 is the relative position of the
eccentric portions. In the spacer 276, the reduced
end portions are coaxial with the axis of the spacer
276 and with the threaded holes that receive the screws
272 and 274; however, a pair of eccentric portions
303a and 305a are provided. The portions 303a and
-22- ~241502
305a are coaxial with each other, but their axis is
offset from the axis of the spacer 276 so that they
are eccentric with respect to the respective portions
303 and 305. Consequently, when the spacer 276 is
rotated, the portions 303a and 305a move eccentrically
about the axis of the spacer 276 to provide the adjust-
ment between the flywheel 226 an the idler wheel
228. This is different from the operation of the
spacer 76 wherein the end portions 103 and 105 are
eccentric with respect to the body of the spacer 76
and the portions 103a and 105a; however, it is not
important which of the reduced diameter portions is
offset from the axis of the spacer, as long as the
two reduced diameter end portions are eccentric with
respect to each other.
Instead of having a pair of set screws such
as the screws 108 and 109 (previously described in
conjunction with FIGS. 8 and 9) to nold the spacer in
position once the spacing adjustment has been jade,
the screws 272 anà 274 (FIGS. 19 and 20) are used to
provide this function. This function is accomplished
my making the lengths of the reduced diameter portions
303 and 305 shorter than the thicknesses of the respec-
tive arms 26~ and 270. Because the reduced diameter
portions 303 ana 305 are shorter than the thickness
of the respective arms 268 and 270, the arms 268 and
270 can be securely wedged between the eccentric por-
tions 303a and 305a and the heads of the screws 272
and 274 (or washers 408 and 410) when the screws 272
and 274 are tightened. Thus, once the spacing between
the idler wheel 228 and the flywheel 226 is adjusted,
the setting of the spacer 276 is maintained by simply
tightening the screws 272 and 274. As a result, the
need for set screws such as the set screws 108 and
109 (FIGS. 8 and 9) is eliminated.
-23- lZ4~502
In accordance with another important aspect
of the present invention, the flywheel 226 (FIG. 27)
need not be fabricated as a unitary structure from a
single material, but can be fabricated from more than
one material. For example, as is illustrated in FIG.
26, the flywheel 226 can have a rim portion 420 fabri-
cated from one material and a hub portion 422 fabri-
cated from another material to provide an optimally
designed flywheel. For example, the rim 420 can be
fabricated from a relatively heavy, durable material,
while the hub portion 422 may be fabricated from a
lighter weight, somewhat resilient material such as
plastic or nylon. By concentrating the heavier
material in the rim 420, a lighter flywheel is obtained.
Also, since it is the mass of the material near the
rim of the flywheel that contributes most to the amount
of energy that can be stored in the flywheel, the
reduction in weight is achieved without sacrificing
the energy storage capability of the flywheel. Also,
the composite flywheel can be of a lower cost than an
all-steel flywheel since less tool steel and less
machining is required.
In addition to reducing the weight and cost
of the flywheel, the use of more than one material
permits an optimum material to be selected for the
rim and hub portions of the flywheel. For example,
the material selected for the rim portion 420 can be
selected for optimum wear qualities, while the material
for the hub 422 can be selected for other qualities,
such as weight, compression and shear strength and
resiliency. In particular, if the hub portion 422 is
fabricated from a hard, but resilient material that
is more compressible than the tool steel used to
fabricate the rim 420, the adjustment of the spacing
between the flywheel 226 and the idler wheel 228
.
~2,~1502
-24-
becomes less critical. As a result, the toggle
mechanism requires less frequent adjustment as the
rim 420 and the ram 244 wear. Suitable materials for
I the hub include rosite, which is a combination of
! 5 polyester and approximately 15~ fiberglass,- hard - -
urethane and other plastics.
Because of the compressibility of the hub
422, when the initial adjustment of the spacing between
the flywheel 226 and idler wheel 228 is made, the
spacing can be made somewhat narrower than could be
tolerated by a system utilizing an all-metal flywheel.
This occurs because the hub 422 will deflect enough
to permit the ram 244 to pass between the flyw`heel
226 and idler wheel 228 when the ram 244 is engaged.
Because the use of a compressible material for the
hub 422 permits a narrower initial setting of the
spacing between the flywheel 226 and the idler wheel
228 to be achieved, the system is less susceptible to
the effects of wear of the rim 420 and the ram 244.
This is because the hub 422 acts as a resilient biasing
device that maintains the rim 420 in contact with the
ram 244 even though both the rim 420 and the ram 244
become thinner through wear. Finally, although the
flywheel 226 is shown to be attached to the shaft 238
Z5 by molding the hub 422 over a pair of hexagonally-
shaped sections 424 and 426 extending from the shaft
238, it should ye understood that the hub 422 could
be screwed on or otherwise attached to the shaft 238.
In the embodiment illustrated in FIG. 25,
the ram 244 also has a lateral crosspiece or travel
limiting stop member 318 affixed thereto. However,
to provide a more secure attachment between the stop
member 318 and the ram 244, and to reduce the prob-
ability of the ram 244 from being dislodged from the
stop member 318 at either the upper or lower limit of
~L~,4150
--2s--
travel of the ram 244, the ram 244 is provided with a
pair of laterally-extending members 428 and 430. The
impact member 318 is molded over the laterally extending
arms 428 and 430, which prevent the ram 24~ frcm slipping
out of the stop member 318 when the stop member 318
impacts the upper bumper 248 or the lower bumper 250.
As previously stated, the fastener dLiving
tool according to the present invention is designed
so that a fastener cannot be driven unless the trigger
100 (or 300) is depressed and the yoke 23 (or 223) is
in contact with a workpiece. If either one of these
conditions is not met, the fastener will not be riven
This function has been achieved in the prior art,
such as in United States Patent No. 4,298,072, by
simply connecting a trigger controlled switch and a
yoke controlled switch in series with the solenoid
and the power line so that the solenoid cannot be
energized unless both the trigger controlled switch
and the yoke controlled switch are closed.
However, when energizing the solenoid, it
is desirable to energize the solenoid with a high
amplitude current of relatively short and preferably
fixed duration. The reason for this is that it is
desirable to for force the ram between the idler wheel
and the flywheel rapidly to assure a proper engagement
of the ram, and then rapidly to retract the armature
of the solenoid to permit the ram to be returned to
its uppermost position without interference from the
- armature of the solenoid.
Therefore, in accordance with yet another
important aspect of the invention, a timing means is
provided to generate the desired pulse. For example,
it has been found that such a current pulse can be
obtained by discharging a capacitor through the
solenoid to thereby rapidly energize the solenoid.
26 ~,AC1502
The capacitor then forms part of a timing circuit or
timing means that automatically terminates the energi-
zation of the solenoid when the capacitor has
discharged.
Several circuits suitable for discharging a
capacitor into the solenoid while preventing the
solenoid from being energized unless both the trigger
and safety yoke is depressed are illustrated in FIGS.
28-31. The circuits illustrated in FIGS. 28-31 are
shown as controlling the operation of the motor 24
and solenoid 84 via the trigger switch 96 and the
yoke controlled switch 98; however, it should be
understood that the circuits can also be used to
control the motor 224 and solenoid 284 via the
switches 296 and 298.
In the circuit illustrated in FIG. 28,
generally designated by the reference numeral 500,
the motor 24 is connected to a source of electrical
power via a contact 96a of the trigger switch 96 and
a fuse 502. Although it is desirable to use an overload
protection device, such as the fuse 502, it should be
understood that the fuse 502 is not necessary for
proper operation of the circuit 500. A charge storage
capacitor 508 is also connected to the electrical
2~ power source via the joke operated switch 98, a current
limiting resistor 504 and a rectifier diode 506. The
capacitor 508 is selectively connected to tne solenoid
98 via the yoke controlled switch 98 and a second
contact 96b of the trigger controlled switch 96. A
transient suppressing diode 512 is connected across
the terminals of the solenoid 84 to reduce switching
transients produced by the inductance of the solenoid
84. A bleeder resistor 510 is connected across the
capacitor 508 to discharge the capacitor when the
tool is not in use.
-27- ~24~5~2
In operation, when the trigger 100 is not
depressed and the yoke is not in contact with a work-
piece, the trigger controlled switch sections 96a and
96b are open, and the yoke controlled switch 98 is in
the position shown in FIG. 28. Consequently, when
the tool is plugged into the electrical power source,
the capacitor 508 is charged via the fuse 502, the
current limiting resistor S04, the diode rectifier
506, and the switch 98. The motor 24 is not energized
under these conditions because the trigger controlled
switch section 96a is open.
When it is desired to drive a fastener into
a workpiece, the trigger 100 is depressed, thereby
closing the switch sections 96a and 96b. The closing
of the switch section 96a energizes the motor 24 to
bring the flywheel 126 up to speed. However, the
solenoid 84 is not energized until the yoke 23 is
brought into contact with the workpiece, at which
time the series path between the capacitor 508 and
the switch 96b is closed via the switch 98, thereby
discharging the capacitor 508 into the solenoid 84.
This energizes the solenoid 84 and causes the solenoid
84 to drive the ram 44 between the flywheel 26 and
the idler wheel 28 to thereby drive the ram 44 into
engagement with a fastener. The length of time that
the solenoid 84 remains energized is determined by
the capacity of the capacitor 508 and the impedance
of the coil of the solenoid 84. Thus, the capacitor
508 and the coil of the solenoid act as a timing circuit
to determine the length of time that the solenoid
will be energized.
After the fastener has been driven, the
yoke 23 is lifted from the workpiece, usually as a
result of the impact produced by the ram 44, and the
armature of the switch 98 is returned to the position
150~
-28-
shown in FIG. 28. This permits the capacitor 508 to
be rapidly recharged so that the next fastener can be
driven when the yoke 23 is again placed in contact
with the workpiece.
If no further fasteners are to be driven,
the trigger 100 is released, thereby opening the switch
sections 96a and 96b. The opening of the switch section
95a opens the circuit between the electrical power
source and the motor 24, and the opening of the switch
section 96b opens the circuit between the capacitor
508 and the solenoid 84. The opening of the switch
section 96b serves as a safety feature to prevent a
fastener from being accidentally discharged should
the fastening tool be set down on its yoke 23 before
the flywheel 26 has come to a complete stop.
Although various size components may be
used as the current limiting resistor 504, the charge
storage capacitor 508 and the bleeder resistor 510,
it has been found that a 100-microfarad capacitor
provides a suitable current pulse to energize the
solenoid 84, and that the use of an 8-ohm resistor as
the current limiting resistor 504 permits the capacitor
508 to be fully recharged between fastener driving
cycles without drawing excessive current from the
electrical power source. A 47,000 ohm resistor has
been found to be suitable for the bleeder resistor
510 since it does not bleed the capacitor 508 between
fastener driving cycles, but discharges it within a
reasonable period of time after trigger 100 has been
released, or after the tool has been disconnected
from the electrical power source.
Another embodiment of the control circuit
500 is illustrated in FIG. 29 and designated by the
reference numeral 500'. In the control circuit 500',
corresponding components have the same reference numeral
2~02
-29-
as their eounterparts in FIG. 28. The components and
operation of the circuit 500 is substantially the
same as that of the circuit 500, with the only excep-
tion being that the switeh element 96b is connected
in series between the switch 98 and the eapaeitor
508, rather than between the switeh 98 and the solenoid
84. Thus, the switeh 96b provides the same safety
funetion as it did in the cireuit 500 of FIG. 28 by
preventing the capacitor 508 from being discharged
into the solenoid 84 when the trigger 100 is not
depressed. However, by being interposed between the
switch 98 and the capacitor 508, the switeh 96b permits
the capaeitor 508 to be eharged only when the trigger
100 is depressee. Thus, the eapaeitor 508 is not
maintained in a charged state whenever the tool is
plugged into an electrical power source as in the
case of the cireuit illustrated in FIG. 28.
FIG. 30 illustrates another variation,
generally designated by the referenee numeral 500 ,
of the circuits 500 and 500 illustrated in FIG. 28
and 29, respeetively. The eireuit 500 illustrated
in FIG. 30 is a simplified version of the eireuit
500 illustrated in FIG. 29, and the same referenee
numeraIs are used to identify eoresponding components
in the two eireuits. In the cireuit 500 illustrated
in FIG. 30, the trigger-operated switch 96 is a single
pole rather than a double pole switch. The single
pole switeh 96 is used to control both of the operation
of the motor 2~ and the charging of the capacitor
508. This is achieved by connecting the switen 96 in
series with both the motor 24, and via other circuitry,
the capacitor 508. The switch 96 is normally open so
that when the trigger 100 is not depressed, the motor
is deenergized and no charging voltage is applied to
eapaeitor 508. When the trigger 100 is depressed,
_30~ 150~,
the switch 96 is closed, thereby energizing the motor
24 and permitting the capacitor 508 to recharge via
the switch 96, the current limiting resistor 504, the
rectifier diode 506 and the yoke operated switch 98.
The capacitor 508 is discharged into the solenoid 84
to effect fastener driving when the yoke 23 is brought
into contact with the workpiece, thereby causing the
switch 98 to elose the cireuit between the capacitor
S08 and the solenoid 84.
The eireuit 500''' illustrated in FIG. 31
is another variation of the eireuit 500" illustrated
in FIG. 30. The eireuit 500''' is similar to the
eireuit 500" except that a seeond switch section 96b'
is used to eonneet a diseharge resistor 514 aeross
the capaeitor 508. The switch section 96b' is similar
to the switch 96b previously discussed except that
the switch section 9~b' is normally closed when the
trigger 100 is not depressed. Consequently, when the
trigger 100 is not depressed, the discharge resistor
214, which has a value of a few ohms, is maintained
eonneeted across the capacitor 508 to maintain the
eapacitor 508 in a substantially discharged condition.
This prevents the capacitor 508 from being accidentally
diseharged into the solenoid 84 should the yoke 23
inadvertently be brought into contact with an object.
Depressing the trigger 100 opens the switch section
196b', and permits the capacitor 508 to be charged
through the fuse 502, eurrent limiting resistor 504
and reetifier diode 506, and permits normal operation
of the fastener driving tool to take place. The bleeder
resistor 510 is not absolutely necessary when the
diseharge resistor 514 is used, but serves as a safety
feature to diseharge the eapacitor 508 in the event
of failure of the switch seetion 96b' or of the resis-
tor 514.
~L2~502
-31~
The circuit shown in FIG. 28 can be modified
to provide a control circuit in which the tool 10 can
be operated by first placing the nosepiece 22 against
a workpiece followed by actuation of the trigger switch
96. More specifically, the contacts 96a of the trigger
switch 96 are shunted or paralleled by a selector
switch, such as a slide switch, which is operated to
close contacts identical in function to the contacts
96a when the tool is to be operated when the pushbutton
is to be actuated last. This maintains the motor 24
continuously energized during the tool operating period.
The yoke 23 is then placed against the workpiece to
operate the switch 98, as described above. When the
pushbutton 100 is then operated to close the contacts
96b, the solenoid 84 is momentarily operated to actuate
the tool 10 as described above.
Obviously, many modifications and variations
of the present invention are possible in light of the
above teachings. Thus, it is to be understood that,
within the scope of the appended claims, the invention
may be practiced otherwise than as specifically des-
cribed above.
