Hold-down device for movable jaw of a vise

A hold-down device for movable jaw of a vise comprises a driving block and a movable jaw member. The driving block is provided with a through hole having therein a rigid sleeve. The movable jaw member comprises therein a drive shaft in such manners that the drive shaft passes through the sleeve and that both ends of the drive shaft are able to rotate. Located between the sliding portion of the driving block and the sliding groove of the vise base is a predetermined clearance, within which the driving block moves upwardly. A screw is permitted to pass through the screw hole of the movable jaw member to press against the side adjacent to the driving block and the screw hole so as to permit the angle formed by the surface of the vise stand and the connection line, which is formed by the contact point of the sleeve and the drive shaft and the drive shaft axial line, to be greater than zero degree and smaller than 90 degrees.

BACKGROUND OF THE INVENTION 
The present invention relates to a vise, and more particularly to a 
hold-down device for movable jaw of a vise. 
The hold-down device for movable jaw of a vise was described in the U.S. 
Pat. No. 2,880,638. As shown in FIG. 1, the hold-down device for movable 
jaw of a vise holds a work piece by making use of the bevel 48 of a 
driving block 46 to exert via a semi-spherical piece 50 a downward 
component force on the movable jaw member 40, which is therefore held down 
so as to keep the holding surface of the vise jaw 68 in a precise vertical 
position in relation to the surface of the vise stand. 
Such hold-down device for movable jaw of a vise of the prior art is 
defective in design in that the neck 49 of the driving block 46 and the 
adjacent area thereof are subjected to a substantial bending stress, which 
is often responsible for the crack of the driving block 46, and that the 
hold-down device is apparently unable to initiate an effective hold-down 
action when the vise is holding the work piece 153 (as shown in dotted 
lines in FIG. 4) in a pulling manner. In other words, the hold-down device 
for movable jaw of a vise of the prior art works only when the vise is 
holding the work piece 153 in a compressing manner. 
SUMMARY OF THE INVENTION 
It is therefore the primary objective of the present invention to provide a 
hold-down device for movable jaw of a vise with means capable of 
minimizing the effect of bending stress on the driving block so as to 
permit the vise to be equipped with a higher vise jaw plate to hold 
securely the work piece having a greater height. 
It is another objective of the present invention to provide the hold-down 
device for movable jaw of a vise with means permitting the hold-down 
device to effect the hold-down action on the movable jaw when the vise is 
holding the work piece in a pulling manner. 
The features and objectives of the present invention will be better 
understood by studying the following detailed description of the preferred 
embodiment, in conjunction with the drawings provided herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 2 and 3, the vise embodied in the present invention is 
shown comprising a driving block 146 having therein a through hole, which 
receives therein a rigid sleeve 147 fitting over a drive shaft 149 capable 
of rotating in the movable jaw 140. Located between the sliding portion 
146A of the driving block 146 and the sliding groove (not shown in the 
drawings) of the vise base is a predetermined clearance, within which the 
driving block 146 moves upwardly. 
In order to use the vise to hold the work piece in a compressing manner, a 
screw 150 is permitted to pass through the screw hole 151 to press against 
one side of driving block 146 so as to allow the driving block 146 to make 
contact with the drive shaft 149 via the rigid sleeve 147. In order to 
generate a hold-down action on the movable jaw under the circumstance 
described above, the bevel angle, which is formed by the line connecting 
the contact point of the rigid sleeve 147 and the drive shaft 149 with the 
drive shaft axial line in relation to the surface of the vise stand, must 
be greater than zero degree and smaller than 90 degrees. Geometrically 
speaking, the size of the bevel angle is dependent on the height 
difference between the axial line of the sleeve 147 and the axial line of 
the drive shaft 149 in addition to the radii of the sleeve 147 and the 
drive shaft 149. As far as the force holding the work piece and the 
hold-down force exerting on the drive shaft 149 by the driving block 146 
are concerned, the bevel angle should be greater if an accurate vertical 
angle of the vise jaw plate in relation to the vise stand is desired. 
Therefore, the vise manufacturer can determine the bevel angle to meet the 
client's specific requirement by means of selecting the relationship of 
the position and the size of the sleeve 147 and the drive shaft 149. As 
shown in FIG. 2, the bevel angle is approximately 45 degrees. 
In addition, a screw hole 154 can be arranged at the end adjacent to the 
movable jaw 140 and the vise jaw plate 152 so as to permit the vise of the 
present invention to hold a work piece 153 in a pulling manner, as shown 
in FIG. 4. The screw 150 can be removed from the screw hole 151 and 
inserted into the screw hole 154 in order to press against the side 
adjacent to the driving block 146. As a result, the hold-down force will 
be exerted on the movable jaw 140 holding the work piece 153 in a pulling 
manner when the vise handle (not shown in the drawing) is rotated. 
The embodiment of the present invention described above is to be considered 
in all respects as merely illustrative and not restrictive. Accordingly, 
the present invention may be embodied in other specific forms without 
deviating from the spirit thereof. For example, the driving block may be 
devoid of the sleeve, and the through hole of the driving block can be 
appropriately hardened. In addition, the cross sections of the through 
hole and the sleeve can be oval or any shape other than circular.