Workpiece supporting device

In a workpiece supporting device for supporting a workpiece, a holding shaft carrying at its one end a center member adapted to support one end of the workpiece is slidably received in a housing. A hydraulic cylinder is formed in the housing and a sleeve member is rotatably mounted on a piston rod of the hydraulic cylinder with a connecting member being threadedly engaged with the sleeve member. A spring is adjustably interposed between the holding shaft and the connecting member and relative axial movement between the holding shaft and the connecting member is limited within a predetermined distance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
The present invention relates to a workpiece supporting device for 
supporting a workpiece by center members. 
2. Description of the Prior Art: 
The conventional workpiece supporting device for supporting a workpiece by 
center members is somewhat satisfactory in performing its intended 
function. However, the device is complicated in construction, thus 
necessarily making it relatively expensive in cost. 
Moreover, since the hydraulic actuator for moving the holding shaft 
carrying the center member toward and away from the workpiece is also 
connected to act on a spring for applying a holding force to the workpiece 
being supported by the center members, the spring is excessively 
compressed each time the hydraulic actuator is operated to retract the 
holding shaft from the workpiece. Therefore, there is a possibility that 
the spring will be damaged by repeated excessive compression. 
Furthermore, such conventional device cannot meet the requirement that the 
holding shaft be accurately adjusted to a desired position for supporting, 
for example, workpieces with the same length but with slightly different 
center bores. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide a new and 
improved workpiece supporting device which is comparatively simple in 
construction and inexpensive in cost. 
Another object of the present invention is to provide a new and improved 
workpiece supporting device wherein a spring for applying a holding force 
to the workpiece being supported by center members has a relatively long 
life. 
A further object of the present invention is to provide a new and improved 
workpiece supporting device wherein a holding shaft carrying a center 
member is accurately adjustable to a desired position. 
Briefly, according to the present invention, these and other objects are 
achieved by providing a workpiece supporting device for supporting a 
workpiece, as mentioned hereinbelow. A holding shaft is slidably received 
in a housing and a center member is carried on one end of the holding 
shaft, adapted to support one end of the workpiece. A hydraulic cylinder 
is formed in the housing and includes a piston slidably received in the 
housing and a piston rod integrally formed with the piston and extending 
from the housing in parallel relationship with the axis of the holding 
shaft. A sleeve member is rotatably but non-slidably mounted on the piston 
rod and formed with a threaded portion at the periphery thereof and a 
device is provided for rotating the sleeve member. A connecting member is 
threadedly engaged with the threaded portion of the sleeve member. An 
adjusting member is threadably engaged with the connecting member in 
coaxial relationship with the holding shaft a spring is interposed between 
the holding shaft and the adjusting member for applying a holding force to 
the workpiece being supported on the center member. A device is also 
arranged between the holding shaft and the connecting member for limiting 
relative axial movement within a predetermined distance. 
In another aspect of the present invention, scale members are arranged 
between the housing and the connecting member for indicating the position 
of the connecting member relative to the housing when the piston is at the 
retracted position thereof. 
In still another aspect of the present invention, an end member is mounted 
on the sleeve member in abuttable relationship with the connecting member. 
A spacing member is pivotably mounted on the connecting member so as to be 
positioned between the connecting member and the end member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings and more particularly to FIGS. 1 and 2 
thereof, a tailstock housing 10 is shown secured to a table 11 by fittings 
13 and bolts 14. A hollow holding shaft 16 carrying a tailstock center 
member 15 at one end thereof for supporting one end of a workpiece (not 
shown) is slidably received in a bore 12 of the tailstock housing 10. The 
other end of the holding shaft 16 projects from the tailstock housing 10 
and faces one side of a connecting member 17. An adjusting bolt 19 which 
engages a nut member 18 secured to the other side of the connecting member 
17 extends through the connecting member 17 to seat a pushing spring 21 
received in a bore 20 of the holding shaft 16. A bolt 22 is threaded into 
the other end of the holding shaft 16 through the connecting member 17 and 
is abuttable at its head portion with the other side of the connecting 
member 17 to limit the axial movement of the holding shaft 16 biased by 
the spring 21 so that a predetermined distance (l) is maintained between 
the holding shaft 16 and the connecting member 17 under the retracted 
state of the holding shaft 16, as best shown in FIG. 1. 
A hydraulic cylinder 23 is formed in the housing 10 within which a piston 
24 is slidably received in parallel relationship to the axis of the 
holding shaft 16. A piston rod 25 extending from the piston 24 rotatably 
supports a sleeve member 26 while being prevented from axial movement. The 
sleeve member 26 is provided with an externally threaded portion 27 which 
engages the connecting member 17. An adjusting member 29 provided with a 
hexagon head 28 is fixed to the end of the sleeve member 26. Accordingly, 
rotation of the adjusting member 29 by the hexagon head 28 causes the 
movement of the connecting member 17 in the direction of the axis of the 
holding shaft 16 through the threaded engagement of the externally 
threaded portion 27 with the connecting member 17 to permit positional 
adjustment of the connecting member 17. End members 30, 31 are 
respectively secured to the opposite ends of the sleeve member 26 to limit 
the movement of the connecting member 17 therebetween. 
As best shown in FIG. 3, a spacing member 35 with a predetermined precise 
width is pivotably received on a shaft 34 which is mounted on the side 
wall of the connecting member 17. A lever 36 is secured to the spacing 
member 35 for manual manipulation thereof. 
The end member 31 is provided with an end face 37 abuttable with the side 
wall of the connecting member 17 and a stepped face 38 spaced a 
predetermined precise distance from the end face 37. Accordingly, the 
connecting member 17 can be accurately positioned at three different 
positions. That is, at a first position, the connecting member 17 is in 
abutting engagement with the end face 37 of the end member 31. At a second 
position the spacing member 35 is positioned between the connecting member 
17 and the end face 37. At a third position, the spacing member 35 is 
positioned between the connecting member 17 and the stepped face 38. This 
adjustment of the connecting member 17 permits the holding shaft 16 to 
support various workpieces with different axial lengths. 
A scale 32 is secured to the housing 10 and an associated reference scale 
33 is secured to the connecting member 17 so that the position of the 
connecting member 17 may be visually observed. As shown in FIG. 2, a dog 
bar 42, slidably received in the housing 10, is secured to a bracket 43 
which is, in turn, secured to the piston rod 25. Dogs 44 and 45 are 
secured to the dog bar 42 to actuate limit switches 46 and 47, 
respectively, for confirmation of forward and backward end positions of 
the holding shaft 16. As shown in FIG. 4, a clamp lever 40 has at the end 
thereof a threaded portion 39 which is in threaded engagement with the 
connecting member 17. A shoe member 41 is received in the connecting 
member 17 between the sleeve member 26 and the threaded portion 39 of the 
clamp lever 40. Accordingly, manipulation of the clamp lever 40 causes 
axial movement of the threaded portion 39 to push the shoe member 41 
toward the sleeve member 26, thereby preventing relative movement of the 
connecting member 17 with respect to the sleeve member 26. 
The operation of the above described device will now be described. FIGS. 1 
and 2 show the piston 24 retracted to its right end position and thus the 
holding shaft 16 is also retracted through the connecting member 17. Under 
this condition, a holding force applied to a workpiece is properly set by 
adjusting compression force of the spring 21, which is performed by 
rotation of the adjusting bolt 19. Thereafter, when the piston 24 is moved 
to the left, the tailstock center member 15 carried by the holding shaft 
16 is moved to the left through the connecting member 17 to support a 
workpiece in cooperation with a headstock center. 
Under normal operations, the aforementioned operations are repeated for 
supporting workpieces with the same axial length. However, when a 
workpiece with different length is to be worked, the following operations 
are required to alter the distance between centers. At first, the shoe 
member 41 is lossened by rotating the clamp lever 40 so as to permit 
rotation of the sleeve member 26 relative to the connecting member 17. 
Thereafter, an operator rotates the hexagon head 28 to move the connecting 
member 17 and holding shaft 16 gradually through the threaded engagement 
of the threaded portion 27 with the connect-in- member 17 and the spring 
21 until a desired distance between center members is nearly obtained 
while observing the scale 32 and the reference scale 33. The lever 36 is 
subsequently swung to position the spacing member 35 within the space 
between the side wall of the connecting member 17 and the end face 37 or 
the stepped face 38 of the end member 31, depending upon the length of the 
workpiece to be supported. The hexagon head 28 is again rotated in the 
reverse direction to tightly position the spacing member 35 between the 
side wall of the connecting member 17 and the end face 37 or the stepped 
face 38 of the end member 31. Accordingly, the holding shaft 16 is 
accurately adjusted to the desired position. Finally, the clamp lever 40 
is rotated to push the shoe member 41 toward the sleeve member 26 for 
preventing the connecting member 17 from moving relative to the sleeve 
member 26. 
While the invention has been described by means of the preferred 
embodiment, it should be understood that the novel characteristics of the 
invention may be incorporated in other structural forms without departing 
from the spirit and scope of the invention. Accordingly, it is to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.