Patent Application
20060226588
1. Field of the Invention
Embodiments of the present invention generally relate to a hand tool and more particularly to a clamp. More particularly still, embodiments of the invention relate to a bar clamp with improved performance and utility.
2. Description of the Related Art
Clamps are used in order to temporarily hold one or more objects so that work can be performed on them. Historically, clamps required two hands in order to work the clamp making it difficult to hold the work piece while clamping. A vast improvement to clamps was made about 15 years ago with the advent of the QUICK-GRIP™ bar clamp, disclosed in U.S. Pat. No. 5,009,134, and QUICK-ACTION™ bar clamp, disclosed in U.S. Pat. No. 4,926,722 to Joseph A. Sorensen and Dwight L. Gatzemeyer. The QUICK-GRIP™ bar clamp provides a single hand clamping tool that allows one free hand to support the work piece or hold other tools and/or materials while clamping the work piece. This is a major improvement over the traditional screw activated “C” clamps or “over center” type lever actuated bar clamps.
However, several problems exist with the QUICK-GRIP™ bar clamp. The QUICK-GRIP™ clamp must balance between the amount of force required by the hand and the amount of movement of the clamp for each squeeze of the hand. The amount of force exerted on the work piece in relation to the force exerted by the hand is determined by the mechanical advantage ratio (MAR) of the mechanism. As the MAR is increased, the amount of force on the clamp is increased, and the amount of force required to squeeze the handle is decreased. However, in the current hand clamps, the distance the clamp travels with each squeeze (or bar index) decreases if the MAR is increased. Thus, the current clamps on the market compromise by providing a MAR of about 4.5:1 and an index distance of 0.2 inches/squeeze. As people get older, the amount of strength in the hand decreases drastically making it more difficult to operate the QUICK-GRIP™ bar clamp or similar products. As the population ages, it is necessary to provide for a clamp that can increase the MAR and the bar index while requiring minimal squeezing force by the operator.
Therefore, a need exists for improved apparatus and methods of hand clamping that increase the force on the workpiece for a primary squeezing force, increase the travel of the clamp per squeeze, and decrease the manufacturing cost.
Embodiments of the invention generally relate to methods and apparatus for clamping a work piece. A clamping apparatus generally includes a stationary jaw disposed on a bar and having a first clamping surface and a moveable jaw disposed on the bar and having a second clamping surface. The apparatus further comprises a drive handle that provides movement of the moveable jaw relative to the bar when operated. The drive handle can be configured to move the clamping surfaces at different rates and forces. For some embodiments, first and second portions of the drive handle pivot about first and second pivot diameters, respectively, such that the moveable jaw moves with different forces. The drive handle can include a drive pin in contact with drive links disposed around the bar to forceably grip and move the bar as the drive pin moves due to operation of the drive handle. In some embodiments, the drive links include a bend in a middle portion thereof so that a first portion above the bar is offset from a second portion below the bar when the drive link is in a non-rotated position with respect to the bar. For some embodiments, a rear handle opposes a force applied to the drive handle and selectively disengages the moveable jaw from the bar upon movement thereof. Further, a release lever can connect a housing of the stationary jaw to the first clamping surface to enable selective disengagement of the stationary jaw from the bar. A method of clamping the work piece comprises moving the drive handle through a first range of motion to move the movable jaw with a first force and moving the drive handle through a second range of motion to move the moveable jaw with a second force smaller than the first force.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The hand clamp 100 further includes first and second clamp heads 9, 29 for gripping a work piece (not shown). Each clamp head 9, 29 includes first and second clamping surfaces 26, 27, respectively. The first clamp head 9 couples to the moveable jaw housing 10 via an arm 30. The second clamp head 29 couples to a stationary jaw housing 11 via a release lever 8. A bar 4 that the jaw housings 10 and 11 are disposed on connects the stationary jaw housing 11 to the moveable jaw housing 10.
The bar 4 includes the first notch 40 and a corresponding second notch 41 on an opposite end thereof for convenience in assembly and manufacturing. The first notch 40 on the bar 4 locks the release lever 8 and attached stationary jaw housing 11 to the bar 4 with the locking dog 15. While the notch 41 is not needed for operation of the bar 4 with respect to the moveable jaw assembly, the notches 40, 41 are symmetrical to enable attachment of the stationary jaw housing 11 to either end of the bar 4 during assembly. This reduces manufacturing and assembly costs.
In operation, a drive link spring 12 disposed within the moveable jaw housing 10 biases the drive handle 5 to remain in an open position with the high reduction pivot diameter 2 engaged with the moveable jaw housing 10 when no outside force is exerted on the drive handle 5. A surface of the movable jaw housing 10 provides a backstop for the drive link spring 12 that acts on the drive handle 5 via drive links 16, shown here as three links, although it should be appreciated there can be any number of links. The drive links 16 have an aperture 50 (visible in
A locking link spring 17 disposed within the moveable jaw housing 10 such that the moveable jaw housing 10 provides a backstop for the locking link spring 17 exerts force on a center portion of the locking link 6. The locking link spring 17 acts to rotate the locking link 6 in a clockwise direction due to a top edge of the locking link 6 being trapped by a cavity formed in the moveable jaw housing 10. The rotation of the locking link 6 causes inside edges of the locking link 6 to normally engage the bar 4 and lock it into place to prevent relative movement between the bar 4 and the moveable jaw housing 10 that is coupled to the locking link 6. Upon squeezing the drive handle 5, the force exerted to move the bar 4 relative to the moveable jaw housing 10 by operation of the drive links 16 is enough to overcome the locking link spring 17 and enable the locking link 6 to release the bar 4. Release of the locking link 6 occurs due to the locking link 6 rotating to a substantially perpendicular position with respect to the bar 4 since movement of the bar 4 with respect to the movable jaw housing 10 having the trapped top edge of the locking link 6 causes counter-clockwise rotation of the locking link 6 against the bias of the locking link spring 17. When the drive handle 5 is released or force is otherwise no longer exerted by operation of the drive handle 5, the locking link spring 17 causes locking link 6 to reengage the bar 4.
When force is first applied to the drive handle 5, the high reduction pivot diameter 2 of the drive handle 5 engages with the moveable jaw housing 10. The MAR is determined approximately by the distance from where the load is applied on the drive handle 5 to the pivot diameter divided by the vertical component of the distance from the drive pin 1 to the pivot diameter. The MAR when the high reduction pivot diameter 2 is engaged is high, for example, about 8:1. It should be appreciated that the arrangement of the drive handle 5, the high reduction pivot diameter 2, and the drive pin 1 can be modified in order to raise or lower the MAR to suit the consumer. The high reduction pivot diameter 2 engages with the drive handle 5 for about half of the full stroke of the drive handle 5. The stroke length required to disengage the high reduction pivot diameter 2 can be modified for a given product. An average human hand produces the maximum squeezing force at the point where the stroke is one half complete. Thus, this embodiment gives the user the maximum clamping force by using a high MAR coupled with the maximum human squeezing force.
In summary, the squeezing force from the user's hand is transmitted to the drive handle 5 to rotate the drive handle 5 about the pivot diameters 2, 7, thereby moving the drive pin 1 which transfers force to the drive links 16 engaging the bar 4 to move the first clamp head 9 toward the second clamp head 29. The drive links 16 have the aperture 50 just slightly larger than the height of the bar 4 to enable the bar 4 to pass through the drive links, as shown in
When the stroke of the drive handle 5 reaches about the half way point, the low reduction pivot diameter 7 of the drive handle 5 engages the moveable jaw housing 10. The high reduction pivot diameter 2 then disengages, as shown in
Once the hand clamp 100 engages the work piece, the locking link 6 holds substantial force in order to prevent the bar 4 from slipping and allowing the movable jaw housing 10 and the clamp head 9 to move away from the stationary jaw housing 11 and clamp head 29. A release mechanism for the locking link 6 is incorporated into the rear handle/lock release 3, as shown in
To release the stationary jaw housing 11 from the bar 4, the user grabs and rotates the release lever 8 clockwise against the bias of the leaf spring 13 to raise the locking dog 15 from the first notch 40. Then, the stationary jaw housing 11 slides freely on the bar 4 to enable removal of the entire stationary jaw assembly. The stationary jaw housing 11 reattaches to the bar 4 by inserting the bar into an opening 42 in the stationary jaw housing 11, as shown in
For some embodiments, the hand clamp 100 can be used as a spreader with the clamping surfaces 26, 27 disposed within the work piece as is known in the art. Unlike the embodiments shown with the clamping surfaces 26, 27 facing one another, the clamping surfaces can accordingly be arranged to oppose one another to facilitate this spreader use of the clamp.
In another embodiment, the drive links 16 can be modified in order to more effectively increase the MAR. In order to increase the MAR, it is necessary for the drive pin 1 to be relatively close to the high reduction pivot diameter 2. This configuration requires the drive pin 1 to push on the drive links 16 at a relatively small distance from the edge of the bar 4. At some minimum distance, the drive links 16 no longer have enough frictional force with the bar 4 to drive the bar. Therefore, drive link(s) 46 provide an improved design that includes offset edges, as shown in
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
