Sequential pivot pin multiplier

A mechanical force enhancement device which both amplified an input force to produce a larger output force while also reducing the speed of an output member during the latter part of the output stroke. The device employs a sequential pivoting operation which is capable of providing the above results while being uncomplicated in its design and construction. The device includes a housing having a pair of spaced-apart camming plates. Each camming plate has a pair of opposing camming contours formed therein so as to define two sets of spaced-apart camming contours. At one end of each camming contour is a recess so as to define two sets of spaced-apart recesses. A linkage member is disposed between the camming plates and includes a driven end adjacent one of the sets of spaced-apart camming contours and a driving end adjacent the other set of spaced-apart camming contours. The linkage member also includes a pair of camming members, each of which engages a corresponding one of the sets of spaced-apart camming contours. The camming members are able to engage their respective recesses only when the other camming member is engaged with its respective camming contours. A stroking device is engaged with the driven end of the linkage member and a rod is engaged with the driving end to reciprocate relative to the housing. A tool can be attached to the distal end of the rod to perform work on a workpiece.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to a mechanical device for the 
enhancement of a linear force, such as a device used to actuate the punch 
of a punch and die set. More specifically, this invention relates to a 
mechanical force enhancer having a link which is sequentially cammed about 
two fulcrums by which a force delivery member is sequentially operated 
between a relatively low force stroke and a slower, relatively high force 
stroke. 
2. Description of the Prior Art 
The prior art discloses a wide variety of mechanical devices which operate 
to mechanically amplify a force which is delivered by hand or by a 
mechanical device such as a fluid cylinder. Generally, such a mechanical 
force enhancer receives as an input a relatively small linear or rotary 
force and amplifies or multiplies it to produce a larger linear force. For 
manufacturing applications, such as a mechanical force enhancer employed 
to operate a punch and die set, the input force is most often generated by 
a fluid driven cylinder or an electric or fluid-driven motor to permit 
some degree of automation. 
An taught in U.S. Pat. Nos. 3,453,914 and 3,680,400 to Lemper et al., an 
input force can be multiplied to produce a larger output force by 
employing an eccentric which is rotated against a ram member carrying a 
tool used to perform work on a workpiece. The force enhancers taught by 
Lemper et al. employ an independently-powered screw mechanism which 
cooperates with the eccentric to incrementally advance the ram member such 
that the output of each device is characterized by an incremental movement 
toward the workpiece coupled with a variable output force at the ram 
member. A disadvantage with the devices taught by Lemper et al. is that 
they are rather complicated in their construction and rely upon two 
separate inputs to produce the force amplification sought. In contrast, 
U.S. Pat. No. 2,390,371 to Ivy teaches a simpler force amplification 
device which employs an eccentric that operates a pair of levers to 
deliver a large linear output force for a punching process. However, the 
mechanical advantage of the eccentric taught by Ivy is rather minor in 
terms of force amplification. 
Mechanical force enhancers are often used to operate a tool which performs 
work on a workpiece, such as a punch and die set noted above. With such 
applications, it is typically preferable that the tool be slowed near the 
end of its stroke to prevent unnecessary impacting of the workpiece. An 
example of such a device is taught in U.S. Pat. No. 4,932,128 to Dacey, 
Jr. Dacey, Jr. teaches a pneumatic cylinder which is mounted to a housing 
having a pair of spaced-apart side plates. The cylinder's piston rod is 
attached to a first end of a link which is guided by one of a pair of 
complementary grooves in the side plates. The second end of the link is 
guided by the second of the pair of complementary grooves, and a ram is 
attached to the link intermediate the first and second ends of the link. 
After the link has been translated a prescribed distance, the second end 
of the link is stopped, forcing the link to pivot about the second end. As 
a result, after the second end of the link is stopped, the speed of the 
ram is decreased and the force input of the cylinder is amplified to the 
ram by the effect of the link rotating about its second end. However, a 
drawback to the force enhancer taught by Dacey, Jr. is that the device is 
rather complicated, the ultimate force output is limited by the relatively 
small size of the link, and the particular structure necessitated by the 
pivot feature of the link is rather complicated, requiring an added level 
of precision. 
As taught in U.S. Pat. No. 3,482,830 to Sendoykas, camming mechanisms are 
also known in the prior art as being useful to alter the output speed of a 
device whose output is in the form of a force. Sendoykas teaches a 
cylinder whose linear input is operated on through a camming device and 
two separate pivots to alter the speed of a clamp. The pivots serve as 
sequential fulcrums about which the body of the clamp pivots as the 
cylinder extends and retracts. However, the output force is not 
intentionally amplified by the device in that the moment created by the 
cylinder about each fulcrum is roughly the same. 
From the above discussion, it can be readily appreciated that the prior art 
does not disclose a mechanical force enhancer which is capable of 
producing an amplified output to a work-performing ram while also being 
uncomplicated in its construction and operation. Nor does the prior art 
disclose such a device which is particularly suitable for use as a punch 
and die press, wherein the output speed of the ram is reduced near the end 
of the stroke to prevent excessive impact loads on a workpiece. 
Accordingly, what is needed is a cost-efficient mechanical force enhancing 
device suitable for use as a punch and die press, the mechanical force 
enhancement device being capable of amplifying an input force and 
delivering the amplified force to a ram member which includes a 
work-performing tool, wherein the force amplification is derived from 
operating the device off two stationary fulcrums which are rugged and 
uncomplicated in their design and which also serve to reduce the output 
speed as the tool nears the workpiece. 
SUMMARY OF THE INVENTION 
According to the present invention there is provided a mechanical force 
enhancement device which both amplifies an input force to produce a larger 
output force acting upon an output member, while also reducing the speed 
of the output member during the latter part of the output stroke. The 
mechanical force enhancement device is capable of providing the above 
results while also being uncomplicated in its design and construction in 
that both the force amplification and the speed reduction are provided 
through sequentially pivoting a linkage upon a pair of fulcrums built into 
a housing which supports both an input device and an output device. 
As a result, the mechanical force enhancement device of the present 
invention is particularly well suited for use with a tool that performs 
work on a workpiece, such as a piercing and clinching device used to 
actuate a punch against a die. With reference to its use with a punch and 
die set, the mechanical force enhancement device essentially relies upon a 
sequential pivot pin multiplier to provide an initial low-force extend 
stroke to the punch, and then later, as the punch draws near to the die, a 
slower, high-force extend stroke. The sequential pivot pin multiplier 
achieves this function by using a linkage member which uses two separate 
fulcrum points to effect the speed and force of the punch relative to the 
die. Though described throughout in terms of its use with a punch and die 
set, it will be apparent that the mechanical force enhancement device of 
the present invention is suitable for a wide variety of other applications 
which rely upon an output force to perform work, whether there is a need 
for only the speed reduction feature, or only the force amplification 
feature, or both. 
The mechanical force enhancement device of the present invention includes a 
housing having at least one camming plate, and more preferably two 
spaced-apart camming plates. Each camming plate has a pair of camming 
contours formed therein so as to define two sets of spaced-apart camming 
contours. At one end of each camming contour there is a fulcrum so as to 
define two sets of spaced-apart fulcrums. The linkage member noted above 
is disposed between the camming plates. The linkage member has a driven 
end between one of the sets of spaced-apart camming contours, and a 
driving end between the second set of spaced-apart camming contours. In 
addition, the linkage member includes a pair of camming members which are 
attached to the linkage member such that a first camming member of the 
pair of camming members is engagable with the first set of spaced-apart 
camming contours and the second camming member is engagable with the 
second set of spaced-apart camming contours. In particular, the camming 
members can engage their respective sets of spaced-apart fulcrums only 
when the other camming member is engaged with its respective set of 
spaced-apart camming contours. 
The mechanical force enhancer also includes a stroking device engaged with 
the driven end of the linkage member for stroking the first camming member 
along the first set of spaced-apart camming contours. An output member, 
such as a rod, is engaged with the driving end to reciprocate relative to 
the housing. A tool, such as a punch, can then be attached to the distal 
end of the rod for performing work on a workpiece. 
In operation, the stroking member strokes the driven end of the linkage 
member while the first camming member is engaged with the first set of 
spaced-apart fulcrums and the second camming member cams the second set of 
spaced-apart camming contours. The output at the driven end of the linkage 
member, and thus at the tool, is characterized as having an output speed 
at some proportion relative to the rate at which the stroking device is 
actuated. Simultaneously, the ratio between the input force of the 
stroking device and the output force at the tool is inverse to the speed 
ratio. The second camming member continues to cam against the second set 
of spaced-apart camming contours until the second camming member 
encounters and engages the second set of spaced-apart fulcrums. At that 
time, the first camming member disengages the first set of spaced-apart 
fulcrums and cams the first set of spaced-apart camming contours. In that 
the linkage member is now being pivoted about the second set of 
spaced-apart fulcrums which is most remote from the input, or driven end, 
of the linkage member, the output at the driven end of the linkage member, 
and thus at the tool, is characterized as having a proportionately lower 
output speed relative to the rate at which the stroking device is 
actuated. However, since the ratio between the input force of the stroking 
device and the output force at the tool is inverse to the speed 
proportion, the output force of the rod is proportionately higher than the 
previous force level. 
According to a preferred aspect of this invention, the force enhancement is 
achieved by the sequential use of two fulcrums which alter the mechanical 
advantage across a linkage member between an input end and an output end. 
As such, the mechanical operation of the device is uncomplicated and, as a 
direct result, highly efficient. The camming members which engage the 
fulcrums are guided to and from the fulcrums by a pair of camming contours 
which ensure smooth and continuous operation of the device. The movement 
of the linkage member can be regulated by added external adjustment which 
limits how far the linkage member can rotate about either or both 
fulcrums. Moreover, the mechanical advantage of the device can be readily 
altered by relocating the fulcrums and relocating the camming members on 
the linkage member. 
In addition, the mechanical force enhancement device of the present 
invention permits the tool to have a large amount of stroke or linear 
movement, enabling it to adapt to workpieces of various thicknesses, while 
also delivering a load of high magnitude at a low rate of application 
during the latter part of the stroke. 
Another significant advantage of the present invention is that the fulcrums 
are formed as integral portions of the camming contours to minimize the 
number of components necessary to perform both the guiding and pivoting 
operations upon the linkage member. Mechanical contact is maintained 
between the camming members and the camming contours such that the output 
of the device is controlled and exhibits a smooth transition between the 
low and high force portions of the output stroke. In addition, with this 
construction and arrangement, the linkage member is the only component 
necessary to transmit the load between the input device and the output 
device such that no additional hardware is necessary to perform the force 
enhancement operation of the present invention. Consequently, the device 
is extremely compact and light compared to force enhancement devices with 
similar load capabilities. 
Accordingly, it is an object of the present invention to provide a force 
enhancement device for amplifying an input force and delivering the 
amplified force to a work-performing output member. 
It is a further object of the invention that the force enhancement device 
be compact and uncomplicated in its construction so as to be versatile for 
use in a typical work environment. 
It is still a further object of the invention that the force enhancement 
device include a linkage member which sequentially rotates about a pair of 
fulcrums such that the output member travels a relatively large distance 
under the influence of a relatively small force, and then travels a much 
shorter distance under a greatly increased force. 
It is another object of the invention that the fulcrums be provided an as 
integral part of a pair of camming contours mounted to a housing within 
which the linkage member is housed. 
It is yet another object of the invention that the force enhancement device 
be suitable as a piercing or punching device for operating a punching or 
piercing member. 
It is still another object of the invention that the force enhancement 
device be constructed so as to be readily adapted to provide different 
output loads and travels for a given input. 
Other objects and advantages of this invention will be more apparent after 
a reading of the following detailed description taken in conjunction with 
the drawings provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference to FIG. 1, there is shown a perspective view of a mechanical 
force enhancement device 10 which employs a sequential pivot pin 
multiplier in accordance with a preferred embodiment of the present 
invention. As illustrated, the mechanical force enhancement device 10 is 
adapted for use as a piercing and clinching device used to actuate a punch 
64 against a die 66. The following description will specifically refer to 
the use of the present invention within the environment of the illustrated 
piercing and clinching device for purposes of clarity so as to assist in 
the understanding of the disclosure. However, the teachings of the present 
invention are not limited to a piercing and clinching device, and can be 
readily adapted by one skilled in the art to a wide variety of other 
operations which rely upon an output force to perform work, whether the 
operation requires only a speed reduction feature, a force amplification 
feature, or both. 
The mechanical force enhancement device 10 includes a housing 12 having a 
number of mounting flanges 54 by which the mechanical force enhancement 
device 10 can be mounted to a suitable support structure (not shown). A 
fluid driven cylinder assembly 14 is mounted to the housing 12. The 
cylinder assembly 14 includes a cylinder rod 16 which is reciprocated by a 
piston (not shown) reciprocably mounted within the cylinder assembly 14. 
The cylinder rod 16 extends into the housing 12 to operate upon the 
internal components of the housing 12 in a manner which will be fully 
explained below. Below the cylinder assembly 14 there is a beam 52 which 
is mounted to the housing 12. A die support beam 58 is mounted and 
projects downwardly from the beam 52. The die support beam 58 is suitably 
provided with a recess (not shown) in which the die 66 is received. 
Longitudinally aligned with the die 66 is the punch 64 which is mounted to 
a rod 18. The rod 18 extends from the housing 12 in a manner essentially 
parallel to the cylinder assembly 14. As seen in FIGS. 2 and 3, the rod 18 
is supported in the housing 12 with a journal bearing 56. Preferably, the 
journal bearing 56 is formed from a suitably rigid material such as 
aluminum and coated with a low friction-wear resistant material, such as a 
suitable grade of Teflon.TM. which is well known in the art. 
Essentially, the mechanical force enhancement device 10 of the present 
invention relies upon a sequential pivot pin multiplier to provide an 
initial low-force extend stroke to the punch 64, and then later, as the 
punch 64 draws near to the die 66, a slower but higher-force extend 
stroke. The sequential pivot pin multiplier achieves this action by 
employing a pivot link 20 which has two spaced-apart camming pins 28 and 
32 which sequentially engage a corresponding pair of fulcrum points to 
determine the speed and force of the punch 64 relative to the die 66. As 
best seen in FIGS. 2 and 3, the pivot link 20 is elongate and has a pair 
of oppositely disposed ends. As viewed in FIGS. 2 and 3, the upper end is 
designated the driven end 36 in that it is driven by the cylinder rod 16, 
while the lower end is designated the driving end 38 in that it drives the 
rod 18. 
Both the driven end 36 and the driving ends 38 have an elongate slot 30 and 
34, respectively. The driven end slot 30 is coupled to the cylinder rod 16 
with a cylinder rod pin 60, while the driving end slot 34 is coupled to 
the rod 18 with a rod pin 62. Preferably, the ends of both the cylinder 
rod 16 and the rod 18 are formed to be yokes (not shown) within which the 
driven and driving ends 36 and 38, respectively, are received. The yoke 
and slot combination permits relative movement between the cylinder rod 16 
and the pivot link 20 and the rod 18 and the pivot link 20 for purposes 
which will become apparent with the further discussion below. Due to the 
sliding action between the driven end and driving end slots 30 and 34 and 
the cylinder pin 60 and rod pin 62, respectively, it is preferable that 
each is hardened to resist wear. 
With continued reference to FIGS. 2 and 3, the camming pins 28 and 32, 
designated the driven end and driving end camming pins 28 and 32, 
respectively, are each guided within a corresponding driven end and 
driving end cam track 42 and 43. Preferably, the camming pins 28 and 32 
are free to rotate so as to reduce friction between them and their 
respective cam tracks 42 and 43. The cam tracks 42 and 43 are formed in a 
side plate 40 mounted to the side of the housing 12. In the preferred 
embodiment, the housing 12 has a pair of spaced-apart side plates 40 
mounted on opposite sides of the housing 12, as can be seen in FIG. 1. In 
addition, each side plate 40 is provided with its own pair of cam tracks 
42 and 43. With this preferred construction, each camming pin 28 and 32 
extends through the pivot link 20, and each of its ends engages one of its 
corresponding cam tracks 42 or 43. The obvious benefit to this symmetrical 
arrangement is that no cantilevered loading of the camming pins 28 and 32 
and of the pivot link 20 occurs, resulting in a more efficient operation 
and better wear characteristics. However, for the sake of clarity the 
remaining detailed description will describe the operation of the 
mechanical force enhancement device 10 with reference only to one side 
plate 40 and its corresponding cam tracks 42 and 43. 
In the preferred embodiment shown in FIG. 5, the driven end driving end cam 
tracks 42 and 43 are integrally formed as a U-shaped contour, with the 
legs of the U-shaped contour serving as the camming portions which the 
camming pins 28 and 32 cam against. A pair of recesses 44 and 46 are 
formed in the end of each leg of the U-shaped contour such that the 
recesses 44 and 46 constitute integral parts of the driven and driving end 
cam tracks 42 and 43, respectively. The recesses 44 and 46 project in 
opposite directions from each other as shown such that they serve as a 
detent in their respective cam tracks 42 and 43. 
The arc of each cam track 42 and 43 is taken from the center of the 
opposing recess 44 and 46 and is approximately the distance between the 
camming pins 28 and 32 such that, as illustrated in FIG. 3, the driving 
end camming pin 32 can cam against its corresponding cam track 43 only 
when the driven end camming pin 28 is engaged with its corresponding 
recess 44. Likewise, the driven end camming pin 28 can cam against its 
corresponding cam track 42 only when the driving end camming pin 32 is 
engaged with its corresponding recess 46, as illustrated in FIG. 4. It is 
important to note that the distance between the camming pins 28 and 32, in 
conjunction with their locations relative to the driven and driving ends 
36 and 38 of the pivot link 20, determines the actual mechanical advantage 
available from the mechanical force enhancement device 10. Accordingly, 
the spacing of the camming pins 28 and 32, along with the corresponding 
cam track contours necessary to match the camming pins 28 and 32, is a 
chief consideration when determining the preferred operating parameters of 
the mechanical force enhancement device 10. 
With reference now to FIG. 4, the pivot link 20 is preferably constructed 
to provide a fixed position for one of the two camming pins 28 and 32 
while biasing the remaining camming pin 28 and 32 to accommodate any 
detrimental tolerancing effects. As a result, each of the camming pins 28 
and 32 remains fully engaged with its respective cam track 42 and 43 
throughout the operating range of the pivot link 20. Moreover, when either 
camming pin 28 or 32 encounters its corresponding recess 44 or 46, the 
camming pin 28 or 32 is positively urged to engage its recess 44 or 46 
such that the other camming pin 28 or 32 is released from its recess 44 
and 46. As illustrated in FIG. 4, the driving end camming pin 32 includes 
a pin locator assembly 22 received in a recess adjacent the driving end 
camming pin 32. The pin locator assembly 22 includes a compression spring 
26 which forcibly biases the driving end camming pin 32 in a longitudinal 
direction away from the driven end camming pin 28. In practice, a spring 
preload of approximately 80 pounds has been found to be sufficient to 
ensure that the camming pins 28 and 32 are properly engaged with their 
respective cam tracks 42 and 43. The pin locator assembly 22 is protected 
from the interior environment of the housing 12 by a retaining plate 24. 
With reference again to FIGS. 2 and 3, the pivot link 20 is provided with 
at least one stop 48 which is adjustably mounted to the housing 12. An 
adjustment screw 50 allows the stop 48 to be easily adjusted, permitting 
the stop 48 to be positioned to selectively limit the movement of the 
pivot link 20 at its driven end 36. In effect, the stop 48 also serves to 
limit the stroke of the rod 18, permitting the mechanical force 
enhancement device 10 of the present invention to be readily adjusted to 
perform a punching or piercing operation on workpieces of various 
thicknesses. 
In a second embodiment shown in FIG. 6, the construction of a mechanical 
force enhancement device 110 is nearly identical to the mechanical force 
enhancement device 10 of the preferred embodiment, a primary distinction 
being a pair of interconnecting links 122 and 124 which function as 
substitutes for the pin locator assembly 22 and the driven and driving end 
slots 30 and 34 of the preferred embodiment. As with the pin locator 
assembly 22, the interconnecting links 122 and 124 accommodate the 
dimensional tolerance effects between the pins 28 and 32 and the cam 
tracks 42 and 43. Moreover, the interconnecting links 122 and 124 allow 
for a significant degree of misalignment between the cylinder rod 16 and 
the driven end 136 of the pivot link 120, and between the rod 118 and the 
driving end 138 of the pivot link 120. The recesses 144 and 146, shown in 
FIG. 6, are similarly located in the cam tracks 142 and 143, as the 
recesses 44 and 46 of FIG. 5. However, the recesses 144 and 146 of the 
second embodiment are not as pronounced as the recesses 44 and 46 of the 
first embodiment, as depicted in FIG. 5. 
The driven end interconnecting link 122 is connected to the cylinder rod 
116 and the driven end 136 of the pivot link 120 with a pair of cylinder 
rod pins 160 and 161, while the driving end interconnecting link 124 is 
connected to the rod 118 and the driving end 138 of the pivot link 120 
with a pair of rod pins 162 and 163. An advantage to this arrangement is 
that the sliding between the cylinder rod pin 60 and the rod pin 62 and 
the driven and driving end slots 30 and 34 of the preferred embodiment is 
eliminated. Accordingly, the potential for wear is also reduced at these 
particular locations. However, a disadvantage with the structure of the 
second embodiment shown in FIG. 6 is that a small percentage of mechanical 
efficiency is lost because the cylinder rod 116 and the rod 118 do not act 
directly upon the pivot link 120. 
Also shown in FIG. 6 is a second stop 148 with a corresponding second 
adjustment screw 150. The second stop 148 is located adjacent the driving 
end 138 of the pivot link 120 to directly limit the stroke of the rod 118. 
In addition, the cam tracks 142 and 143 are shown as being machined 
entirely separately into the side plate 140. However, the operation 
associated with the second embodiment remains essentially identical to 
that of the first. 
In the operation of both the first and second embodiments of the present 
invention, the cylinder assembly 14 is driven by a suitable fluid, such as 
air at typical shop pressures of about 75 psi. Under the influence of the 
air, the cylinder rod 16 extends, thereby stroking the driving end camming 
pin 32 along the driving end cam track 43 while the driven end camming pin 
28 is trapped in its recess 44, as seen in FIG. 2. Accordingly, the recess 
44 defines a first fulcrum point about which the pivot link 20 rotates 
during the first part of the stroke. During this time the driving end 
camming pin 32 is forced to follow its cam track 43 toward its 
corresponding recess 46. Also during this portion of the stroke, the 
output at the rod 18 can be characterized as being relatively rapid and 
low force because the cylinder rod 16 is operating upon a shorter 
cantilever relative to the first fulcrum (the driven end recess 44), and 
the output, as embodied in the rod 18, is located on a longer cantilever 
relative to the first fulcrum. 
Once the driving end camming pin 32 encounters its recess 46, it is forced 
into the recess 46 by the operational forces induced by the cylinder rod 
16 and the pin locator assembly 22. Simultaneously, the driven end camming 
pin 28 drops out of its corresponding recess 44, and thereafter follows 
its driven end cam track 42, as seen in FIG. 3. As a result, the driving 
end pin 32 and its recess 46 together define a second fulcrum point about 
which the pivot link 20 rotates during the latter part of the stroke. 
During this portion of the stroke, the output at the rod 18 can be 
characterized as being relatively slow and high force because the cylinder 
rod 16 is operating upon a longer cantilever relative to the second 
fulcrum (the driving end recess 46), and the output, as embodied in the 
rod 18, is located on a shorter cantilever relative to the second fulcrum. 
As a result, the operation of the mechanical force enhancement device 10 of 
the present invention provides a two-stage operation. During the first 
stage as the punch 64 is being brought into position, the first fulcrum 
permits the punch 64 to approach the die 66 rapidly. Thereafter, as the 
punch 64 draws nearer to the die 66, the second stage of operation begins, 
wherein the pivot link 20 pivots upon the second fulcrum to provide a much 
slower but greatly increased force. The slower stroke, as the punch 64 
meets the die 66, ensures that excessive impact loading will be minimized. 
Accordingly, a significant advantage of the mechanical force enhancement 
device 10 of the present invention is that mechanical force enhancement is 
achieved by the sequential use of two fulcrums which alter the mechanical 
advantage across the pivot link 20 between an input end (the cylinder rod 
16) and an output end (the rod 18). This structure provides for mechanical 
operation which is uncomplicated and, as a direct result, highly 
efficient. The fulcrums are advantageously provided as the recesses 44 and 
46 in the pair of cam tracks 42 and 43, such that each camming pin 28 and 
32 are guided into and out of engagement with its respective recess 44 and 
46. The movement of the pivot link 20 is regulated by the stop 48 which 
limits how far the pivot link 20 is permitted to rotate about either 
fulcrum. 
In addition, the mechanical force enhancement device 10 of the present 
invention permits a tool to have a large amount of stroke or linear 
movement during a first stage of operation, enabling the mechanical force 
enhancement device 10 to be adapted to workpieces of various thicknesses, 
while also delivering a load of high magnitude at a low rate of 
application during the latter part of the stroke. Moreover, the mechanical 
advantage of the mechanical force enhancement device 10 can be readily 
altered by replacing the side plates 40 with ones that have the recesses 
44 and 46 relocated to define different fulcrum locations. The pivot link 
20 can then be replaced with one in which the camming pins 28 and 32 are 
relocated to correspond with the new locations of the recesses 44 and 46 
in the side plates 40. 
Another significant advantage of the present invention is that the 
fulcrums, as recesses 44 and 46, are formed as integral portions of the 
cam tracks 42 and 43 in a manner that minimizes the number of components 
necessary to guide and pivot the pivot link 20 in the preferred manner 
described above. Mechanical contact is maintained between the camming pins 
28 and 32 and the cam tracks 42 and 43 such that the output of the 
mechanical force enhancement device 10, as observed in the rod 18, is 
controlled and exhibits a smooth transition between the low and high force 
portions of the output stroke. In addition, with the construction and 
arrangement of the mechanical force enhancement device 10 of both 
embodiments, the toggle link 20 is the only component necessary or 
desirable to transmit the load between the cylinder rod 16 and the rod 18 
such that no additional hardware is necessary to achieve the force 
enhancement operation of the present invention. Consequently, the device 
is extremely compact and lightweight compared to devices with similar load 
capabilities. 
Accordingly, the present invention provides a mechanical force enhancement 
device 10 which amplifies an input force to produce a larger output force 
acting upon an output member, while also reducing the speed of the output 
member during the latter part of the output stroke. The mechanical force 
enhancement device 10 employs a sequential pivoting operation which is 
capable of providing the above results while being uncomplicated in its 
design and construction. The mechanical force enhancement device 10 of the 
present invention is particularly well suited for use with a tool that 
performs work on a workpiece, such as a piercing and clinching device used 
to actuate a punch 64 against a die 66. Though described herein in terms 
of its use with a punch and die set, the mechanical force enhancement 
device 10 of the present invention is also suited to perform a wide 
variety of other operations which rely upon an output force to perform 
work. 
While the invention has been described in terms of a preferred embodiment, 
it is apparent that other forms could be adopted by one skilled in the 
art. Accordingly, the scope of the invention is to be limited only by the 
following claims.