Adjustable spring clamp

An adjustable clamp includes first and second gripping members pivotally coupled to each other for movement about a pivot pin, a helically coiled spring having a tubular portion disposed around the pivot pin having first and second end extensions extending from the tubular portion for biasing the gripping members toward a gripping position, and a bar having a threaded aperture, a threaded member, and a bracket, the bar being positioned between the helically coiled spring first end extension and the first gripping member, the bracket being coupled to the first gripping member and the threaded member rotatably engaging the bracket and the bar, the bar being movable relative to the bracket in response to rotation of the threaded member so as to reposition the first and second end extensions relative to each other thereby adjusting the force applied by the spring against the gripping members. An elastomeric member covers the end of the lever arms remote from the jaws, and an end portion of a support stand is received between one of the lever arms and the elastomeric member covering said lever arm, a support member extending downwardly from said end portion to a generally trapezoidal base member unitary with the support member further including non-skid means for reducing movement of the base member relative to a work surface.

BACKGROUND OF THE INVENTION 
The present invention relates to clamps and particularly to spring clamps 
having a spring for biasing the clamps toward a closed position. More 
particularly, the invention relates to clamps with an adjustment mechanism 
for adjusting the bias of the spring. 
Spring clamps are well known in the art and come in a wide range of 
gripping strengths. For example, at one end of the spectrum, some clamps 
are quite large with enormous strength for holding large workpieces in 
various industrial manufacturing and repair applications. At the other end 
of the spectrum, home hobbyists use relatively weak clamps for holding 
small parts when assembling plastic models or the like. 
Unfortunately, in many instances a particular clamp may be too strong (or 
weak) for a desired application. For example, an industrial strength clamp 
would crush the hobbyist's small plastic part, and is therefore unusable 
in the hobbyist application. Moreover, even in a particular situation, 
such as a workshop, a worker might have need for various gripping 
strengths, requiring separate clamps. 
Maintaining an assortment of clamps for holding a variety of workpieces to 
cover a variety of jobs that a workman might be called upon to perform can 
be very costly. Thus, a single clamp that can be adjusted for use in a 
wide variety of applications would be very useful. A adjustable spring 
clamp that is economical to produce yet includes a simple and effective 
mechanism to adjust the amount of gripping strength would be very useful 
clamp and would be welcome by users. 
SUMMARY OF THE INVENTION 
According to the present invention, an adjustable clamp comprises first and 
second gripping members coupled together for pivotal movement about a 
pivot pin between a gripping position and a releasing position and force 
applying means, coupled to the pivot pin and the gripping members, for 
applying a closing force to the gripping members. The clamp further 
includes means for repositioning the force applying means to change the 
amount of the closing force. 
The first and second gripping members include first and second jaws and 
first and second lever arms, respectively. The lever arms extend from the 
jaws, with the jaws and lever arms positioned on opposite sides of the 
pivot pin. The force applying means includes a spring wrapped around the 
pivot pin and having first and second end extensions positioned to engage 
the first and second lever arms, respectively. 
The repositioning means includes a cylindrical bar having a threaded 
transverse bore, a bracket attached to the first lever arm, and a threaded 
member rotatably coupled to the bracket and threadedly coupled to the bar. 
The bar is positioned between the first end extension of the spring and 
the first lever arm, and the threaded member extends between the bracket 
and the bar, so that rotation of the threaded member moves the bar 
relative to the first lever arm. As the bar moves, it engages the first 
end extension of the spring, causing the first end extension to move 
relative to the second end extension. The relative movement between the 
first and second end extensions increases or decreases the tension in the 
spring, and therefore changes the force that the spring applies to the 
lever arms. 
A support stand can be coupled to the first gripping member for holding the 
clamp in a predetermined orientation. The preferred support stand includes 
a generally trapezoidal base member having a first edge and a support 
member coupled to the base member at the first edge. The support member 
includes a generally trapezoidal lower portion and a generally rectangular 
upper portion extending upwardly from the lower portion. The rectangular 
upper portion is configured to engage the clamp. Non-skid pads for 
reducing movement of the base member relative to a work surface are 
attached to the bottom of the base member. 
Additional objects, features, and advantages of the invention will become 
apparent to those skilled in the art upon consideration of the following 
detailed description of a preferred embodiment exemplifying the best mode 
of carrying out the invention as presently perceived.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An adjustable spring clamp 10 constructed according to the present 
invention is illustrated in FIGS. 1-4. The adjustable spring clamp 10 
includes a conventional clamp 12 having a coil spring 14 for biasing the 
clamp 12 toward a gripping position shown in the drawings and an 
adjustment mechanism 16 for changing the tension of the spring 14 to 
adjust the bias of the spring 14, and therefore, the gripping strength of 
the clamp 12. 
The conventional clamp 12 includes first and second gripping members 18 and 
20 pivotally coupled to a pivot pin 22. The gripping members 18 and 20 
include first and second gripping jaws 24 and 26 and first and second 
lever arms 28 and 30 extending from the jaws 24 and 26, respectively. 
Brackets 32 and 34 extend from either side of each of the lever arms 28 
and 30 and include pivot pin receiving apertures 36. The brackets 32 and 
34 are positioned to overlap each other and align the pivot pin receiving 
apertures 36. 
The clamp 12 further includes a force applying means in the form of a 
helically coiled spring 14 includes a coiled portion 38 forming a tube 44 
and first and second end extensions 40 and 42 projecting from the tube 44. 
The tube 44 is disposed between the brackets 32 and 34 so as to align the 
interior of the tube 44 with the apertures 36 in the brackets 32 and 34. 
The pivot pin 22 extends between the apertures 36 and through the interior 
of the tube 44 to hold the spring 14 in position relative to the jaws 24 
and 26 and lever arms 28 and 30. The end extensions 40 and 42 project 
generally away from the jaws 24 and 26 and engage the lever arms 28 and 
30. The tension in the spring 14 biases the lever arms 28 and 30 to move 
apart, thereby urging the jaws 24 and 26 toward each other and the 
gripping position illustrated in the figures. 
The adjustment mechanism 16 for changing the tension of the spring 14 
includes a bracket 50, a cylindrical bar 52, and a threaded member 54 
rotatably coupled to the bracket 50 and the bar 52 which together form a 
repositioning means. The bracket 50 includes a lever-arm engaging portion 
56 and a threaded-member engaging portion 58. As illustrated in the 
figures, the lever-arm engaging portion 56 is positioned adjacent the 
inside surface 60 of the first lever arm 28, and is attached thereto by a 
rivet 62 or other suitable fastening means. The threaded-member engaging 
portion 58 includes a threaded-member receiving aperture 62 and extends at 
an angle 64 from the lever-arm engaging portion 56. 
The cylindrical bar 52 includes a longitudinal axis disposed in parallel 
spaced-apart relation to the pivot pin 22 and a threaded transverse bore 
68 having threads 70. The bar 52 extends between the brackets 32 and 34 
and is positioned between the first extension 40 of the spring 14, which 
is shorter than extension 42, and the inside surface 60 of the first lever 
arm 28. 
The threaded member 54 includes a head 72 and a threaded shaft 74 having 
threads 76 configured to engage the threads 70 of the transverse bore 68. 
The head 72 is sized to prohibit the head 72 from passing through the 
aperture 62, while the shaft 74 is sized to allow the shaft 74 to pass 
through the threaded-member receiving aperture 62. 
The angle 64 is predetermined so as to dispose the threaded member 54 
perpendicular to the threaded-member engaging portion 58 and parallel to 
the lever arm 28. As illustrated in the figures, the threaded shaft 74 
passes through the aperture 62 and extends generally toward the jaws and 
parallel to the lever arm 28. The threaded shaft 74 engages the threads 70 
of the transverse bore 68 of the bar 52 to couple the bar 52 to the 
bracket 50. 
In operation, the threaded shaft 74 engages the threads 70 of the 
transverse bore 68 so that the bar 52 is pulled toward the bracket 50 in 
response to clockwise rotation of the threaded member 54. As the threaded 
member 54 is rotated, the bar 52 is pulled under the first end extension 
40, pushing the first end extension 40 away from the inside surface 60 of 
the lever arm 28, as illustrated in FIG. 2. Thus, the first end extension 
40 is repositioned toward the second end extension 42, effectively winding 
the coil spring 14 and thereby increasing the force that the spring 14 
applies to the lever arms 28 and 30. 
When the threaded member 54 is rotated in the counterclockwise direction, 
the tension of the spring 14 acts against the bar 52 to urge the bar 52 to 
move away from the bracket 50. As the bar 52 moves away from the bracket 
50, as illustrated in FIG. 3, the first end extension 40 is repositioned 
away from the second end extension 42. As the first and second end 
extensions 40 and 42 move apart, the tension in the spring 14 is 
decreased, and less force is applied to the lever arms 28 and 30. Thus, 
the cooperation of the bracket 50, the bar 52, and the threaded member 54 
provide a simple, yet effective, means to adjust the bias applied by the 
spring 14. 
A support stand 80, such as illustrated in FIG. 4, can be used to support 
the adjustable clamp 10. As illustrated in FIG. 5, the clamp 10 can be 
maintained in one of two positions by the stand 80 so as to orient the 
workpiece and free the hands of the user. The stand 80 includes a base 
member 84 and a support member 86 which is integrally formed with the base 
member 84 and bent to project upwardly therefrom. The support arm 86 
includes a generally rectangular portion 88 for engaging the clamp 10. The 
rectangular portion 88 includes first and second surfaces 90 and 92 and 
has substantially the same width as the lever handles 28 and 30. A 
plurality of non-skid pads 94 are attached to the bottom of the base 
member 84 to prevent the support stand 80 from sliding on a work surface. 
Elastomeric covers 74 and 76 are coupled to the ends of the lever arms 28 
and 30 and to the jaws 24 and 26, respectively. The elastomeric covers 74 
and 76 are provided to furnish a comfortable grip while electrically 
insulating the lever arms 28 and 30 and to prevent the jaws 24 and 26 from 
marring any article held therein. One of the covers 74 on the lever arms 
28 and 30 can include an aperture 78 (FIG. 2) formed in the end of the 
cover 74. 
As illustrated in FIGS. 2 and 5, the rectangular portion 88 of the support 
arm 86 can be inserted into the aperture 78 and sandwiched between the 
lever arm 28 and the elastomeric cover 74, with the first surface 90 
positioned against the lever arm 28. The cover 74 and lever arm 28 
cooperate to grip the rectangular portion 88, so that the clamp 10 is 
maintained in position relative to the base stand 80. The rectangular 
portion 88 can also be inserted into the aperture 78 with the second 
surface 92 positioned against the rectangular portion 88, as seen in 
phantom in FIG. 5. This allows the user to alter the orientation of the 
clamp 10 and any workpiece held by the jaws 24 and 26. Thus, the base 
stand 80, the lever arms 28, and the elastomeric cover 74 cooperate to 
maintain the clamp 10 in a desired orientation, which can be easily 
changed by removing the clamp 10 from the base stand 80, rotating the 
clamp 10 about lever arm 28, and reinserting the support arm 86 into the 
aperture 78. 
Although the invention has been described in detail with reference to a 
certain preferred embodiment, variations and modifications exist within 
the scope and spirit of the invention as described and defined in the 
following claims.