United States Patent David W. Cosner Rte. 1, Greenwood, Mo. 64034 2! Appl. No. 829,310
 Filed June 2,1969
 Patented June 29,1971
 inventor s4 CLAMPINC DEVICE 2 Claims, 3 Drawing Figs.
 US. Cl .I 269/241,
269/249, 248/354 S, 85/1 SS  Int. Cl B25b 5/10  Field of Search 169/24 1 249; 248/354 S; 85/1 SS 3,055,654 9/1962 Harrison 269/241 FOREIGN PATENTS 4 136,286 1961 U.S.S.R. 248/354 S Primary Examiner-Andrew R. Juhasz Assistant Examiner- Donald D. Evenson Attorne v--Fishburn, Gold and Litman ABSTRACT: A clamping device for holding a workpiece between an anvil surface and a movable workpiece-engaging member has a threaded adjustment shaft received in a threaded sleeve portion of a frame for moving the workpieceengaging member toward and away from the anvil surface. The workpiece-engaging member is mounted on one end ofa rod having the other end threadedly received in a recess in one end of the threaded adjustment shaft and the threads on the shaft and rod are of the same hand and of different leads whereby relative movement between the shaft and rod occurs upon continued rotation of the shaft after the workpiece-engaging member engages the workpiece.
PATENTEU JUN29I971 3, 589,708
ivwnnmml INVENTOR. D mad W Cosner ATTORNEYS CLAMPING DEVICE The present invention relates to clamping devices and more particularly to C-clamps adapted to exert high holding or clamping force.
The principal objects of the present invention are: to provide a clamping device of the C-clamp type adapted to exert high clamping or holding force on a workpiece with minimum torque applied to a screw shaft having a workpiece engaging member mounted on one end of a threaded rod having the other end received in a threaded recess in one end of the threaded shaft whereby there is relative movement between the shaft and the rod after the workpiece engaging member engages the workpiece and the screw adjustment shaft is moved toward the workpiece; to provide such a clamping device wherein the threads on the screw adjustment shaft and threaded rod are of the same hand and the lead of the rod threads is lesser than the lead of the shaft threads whereby the holding or clamping force is increased by the relative movement between the rod and shaft; and to provide such a clamping device which is economical to manufacture, simple to operate, durable in construction, and particularly well adapted for the proposed use.
Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein are set forth by way of illustration and example certain embodiments of this invention.
FIG. 1 is a side elevational view of a clamping device embodying features ofthe present invention.
FIG. 2 is an enlarged fragmentary sectional view taken on line 22, FIG. 1, showing the relation between an adjustment shaft and a workpiece-engaging member.
FIG. 3 is a side elevational view of a modified clamping device for use with wrenches.
Referring more in detail to the drawings:
The reference numeral 1 generally designates a clamping device for holding a work piece 2 in clamping engagement with any suitable work surface or table 3. The clamping device 1 has an anvil surface 4 engageable with the work surface 3 and a workpiece engaging member 5 movable toward and away from the anvil surface 4 for holding the work piece 2 therebetween.
The clamping device 1 has a frame 6 which is generally C- shaped, having a base portion 7 extending between an adjustment arm 8 and an anvil arm 9 illustrated as upper and lower arms, respectively, in FIG. 1. The anvil arm 9 has the anvil surface 4 at the free end thereof and the adjustment arm 8 has a sleeve portion 10 at the free end thereof. The sleeve portion 10 is internally threaded to receive an elongated externally threaded adjustment shaft 11 for longitudinal movement through the sleeve portion 10. The adjustment shaft 11 has one end 12 thereof adjacent the anvil surface 4 and in an opposed relation therewith. The adjustment shaft 11 has an internally threaded recess 13 opening from the one end 12 thereof for receiving the work-engaging member 5, as later described. The adjustment shaft 11 has means for rotating same and in the illustrated structure the other end of the shaft 11 has a gripping means thereon for turning the shaft 11, thereby moving the work-engaging member 5 toward or away from the anvil surface 4. In the illustrated structure, the gripping means is illustrated as diametrically opposed levers 14 extending radially outwardly from an upper end of the adjustment shaft 11.
The workpiece-engaging member 5 is illustrated as an externally threaded rod 15 extending from a head portion 16 with the rod 15 being threadedly received in the recess 13 whereby in response to relative rotation of the rod 15 and shaft 11 the head portion 16 may move longitudinally of the adjustment shaft 11. The head member 16 is illustrated as having a planar workpiece-engaging surface positioned in an opposed relation to the anvil surface 4 whereby the anvil surface 4 and the workpiece-engaging member 5 cooperate to hold a workpiece 2 in clamping engagement with a suitable work surface or table 3.
It is desirable to provide a clamping device adapted to exert maximum clamping force or pressure in response to minimum torque applied to an adjustment member. Therefore, the
between the work piece engaging member 5 and the adjust-- ment shaft 11. it is desirable that this relative movement increase the clamping force, therefore, the lead of the threads on the rod 15 is less than the lead of the threads on the adjustment shaft 11.
it is noted that the farther apart the lead ratio the less the mechanical advantage thereof, and the closer the two leads become, the greater the mechanical advantage until the two leads are the same, at which point the relative movement between the head portion 16 and the one end 12 of the adjustment shaft 11 no longer occurs. It is also noted that the closer the lead ratios the lower the torque required to turn the adjustment shaft 11 to move the one end 12 thereof toward the head portion 16.
in use, the head portion 16 is spaced from the one end 12 of the adjustment shaft 11 and the anvil surface 4 is engaged with a lower surface of a suitable work table 3 or the like, with the workpiece 2 mounted or positioned thereon. The levers 14 are turned to move the head portion 16 into engagement with the workpiece 2. Continued turning of the levers 14 after engagement of the head portion 16 with the workpiece 2 holds the head portion 16 in a nonturning position and moves the one end 12 of the adjustment shaft 11 toward the head portion 16, thereby accomplishing relative movement therebetween. This relative movement increases the clamping force exerted by the head portion 16 and the anvil surface 4 on the worktable 3 and workpiece 2.
FIG. 3 illustrates a modified clamping device 17 having a modified adjustment shaft '18 mounted in the sleeve portion 10 of the adjustment arm 8. The modified adjustment shaft 18 has a gripping portion 19 on an upper end thereof adapted to be gripped by a suitable wrench 20, such as an end wrench, pipe wrench or the like.
The use of the modified clamping device 17 is substantially similar to the clamping device 1 except that greater leverage may be obtained through the use of wrenches 20 or the like engaging the gripping portion 19 thereby increasing the clamping force holding the workpiece 2 in engagement with the worktable 3 and between the workpiece-engaging member 5 and the anvil surface 4.
It is to be understood that, while I have illustrated and described certain forms on my invention, it is not to be limited to these specific forms or arrangement of parts herein described and shown.
1. A clamping device comprising:
a. a frame having a stationary anvil surface and an elongate sleeve portion spaced from said anvil surface, said sleeve portion having an axial bore with internal helical screw threads, the longitudinal axis of said bore substantially perpendicular to said anvil surface,
b. an elongate movable member having a shaft extending through said sleeve portion bore with one end toward and spaced from said anvil surface, said shaft having external helical screw threads engaged with and cooperating with said screw threads in the sleeve portion bore, said screw threads having a selected inclination with respect to the longitudinal axis of the sleeve portion bore whereby the shaft is moved toward the anvil surface in response to rotation in one direction, said shaft having an axial bore extending therein from said one end,
0. internal helical screw threads in said shaft bore and having an inclination relative to said longitudinal axis in the direction of the inclination of the external screw threads on the shaft and of lesser lead,
. a workpiece-engaging head having an elongate shank exwhereby the rotation of the head stops on clamping engagement with said workpiece and continued rotation of the movable member in said one direction provides a differential screw action increasing the clamping force on the workpiece.
. A clamping device as set forth in claim 1 wherein: the frame is C-shaped with the anvil surface at the end of one arm and the sleeve portion is at the end of the other arm,
. a lever means is on said movable member for rotating same to move the shaft longitudinally in the internally threaded bore of the sleeve portion.