PRESSURE ASSEMBLIES

ENSEMBLES PRESSEURS

English Abstract

ABSTRACT
A pressure assembly comprises a base plate, a ram and a wedge
located between the base plate and the ram, the wedge having an inclined
face facing the base plate or ram, the facing surface of the base plate or
ram being inclined at the same angle and a screw adapted to move the wedge
at right angles to the separation of the ram and base plate to alter the
separation of the ram and base plate. Preferably a pair of wedges are provided,
and preferably their inclined faces are oppositely-inclined. The pressure
assembly may be used in conjunction with a support member adapted to be
secured to a firm foundation, for example by bolts passing through bores.
The assembly can be used to clamp a workpiece between the ram and a fixed
member by engagement of the base plate with the fixed member and by
increasing the separation of the ram from the base plate by rotating the screw.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A pressure assembly comprising a base plate, a ram, and a pair
of wedges located between the base plate and the ram, the wedges having
oppositely inclined faces facing the base plate or the ram, the facing
surface of the base plate or ram being inclined at the same angle, a thrust
bearing fixedly mounted relative to the base plate or the ram at one end
thereof,and a screw supported in said thrust bearing for rotation and adapted
to move the wedges symmetrically in opposite directions at right angles to
the separation of the ram and base plate such that rotation of said screw
alters the separation of the ram and base plate.
2. An assembly as claimed in claim 1 wherein said screw has portions
of oppositely-directed threads for moving said wedges in opposite directions.
3. An assembly as claimed in claim 1 wherein said screw has three
threaded portions of different pitches, the portion of intermediate pitch
engaging a threaded bore in said thrust bearing and the other portions
engaging respective wedges, the difference between the pitches being equal.
4. An assembly as claimed in claim 1 comprising means to secure the
ram and the base plate to the wedges to prevent relative movement between the
wedges on the one hand and the ram and the base plate on the other hand in
the direction of the separation of the ram and base plate.
5. An assembly as claimed in claim 4 wherein said securing means com-
prises lugs and grooves which engage each other and which run longitudinally
on said base plate, wedges and ram parallel to the axis of the screw.

6. An assembly as claimed in claim 5 wherein said lugs and grooves
are dovetail-shaped.
7. An assembly as claimed in claim 5 wherein said grooves are
provided with replaceable bearing plates along a surface engaging said lugs.
8. A clamping device comprising a support member adapted to be
secured fixedly to a firm foundation and a pressure assembly as claimed in
claim 1, said base plate being secured against a face of said support member.
9. A device as claimed in claim 8 wherein said support member is
formed with fixing holes through which bolts may pass to secure the support
member to a firm foundation and means on said support member for adjusting
the inclination of the line joining the fixing holes to said face of said
support member.
10. A device as claimed in claim 9 wherein said support member is formed
with three fixing holes, said inclination adjusting means being arranged to
adjust two of the holes independently relative to the third so that the holes
lie either in a single line of variable inclination to said face or at the
corners of a triangle.

Description

This invention relates to a pressure assembly comprising a base
plate and a ram and means for moving the pla-te relative to -the ram. In a
screw clamp, -the screw acts as the moving means and one turn oE the screw
causes the base plate and the ram -to change their separa-tion by the pi-tch
of -the screw. The pressure which can be exerted by -the base plate and
the ram is limited by the s-trength of the screw.
According to the invention, there is provided a pressure assembly
comprising a base plate, a ram, and a pair of wedges located between the base
plate and the ram, the wedges having oppositely inclined faces facing the
base plate or the ram, the facing surface of the base plate or ram being ~ :
inclined at the same angle, a thrust bearing fixedly mounted relative to the ;
base plate or the ram at one end thereof, and a screw supported in said
thrust bearing for rotation and adapted to move the wedges symmetrically in
opposite directions at right angles to -the separation oE the ram a~d base
plate such tha-t rotation of said screw alters the separation of the ram and
base plate. : ~
The pressure assembly may be used in conjunction with a support ~ .
member against which the base plate or the ram may be placed so that
pressure may be exerted on a workpiece placed against the o-ther of the base
plate and ram on movement of the wedge in the pressure assembly.
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An example of the invention will now be described wi.th reference
to the accompanying fi~jure, which is an isometric partially exploded view
of a pressure assembly, suppor-t cas-ting and face plate.
The pressure assembly shown in the Elgure comprises a base plate
11 and a ram 12 having outwardly facing parallel surl-aces whose separation
can be adjusted. If fixed members 13 and 14 are provided with inwardly
facing parallel surfaces, the pressure assembly can be placed for example
with the surface of base plate 11 engaging the fixed member 13 and the
separation between the base plate and the ram can be increased to clamp a
workpiece be-tween .
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the surface of the ram 12 and -the fixed member 14.
The base plate 11 is a parallel-sided member with a
dovetail-shaped groove 21 on the side facing the ram 12.
The ram 12 has a pair of inclined surfaces 22 and 2~ arranged
symme-trically facing the base pla-te 11 and each surface
22 and 23 has a dovetail-shaped groove 2~ formed therein.
A pair of wedges 25 and 26 are arranged between the
base plate 11 and the ram 12 9 the wedges having surfaces
inclined at the same angle as the surfaces 22 and Z3
and facing those surfaces. The wedges 25 and 26 have
dovetail-shaped projections (not visible) on both sides
for running in the grooves 21 and 24 so -that the facing
surfaces of the wedges with the base plate 11 and with
the ram 12 are kept in engagement although the wedges can
move at right angles to the separation of the ~ase plate 11 :
from the ram 12.
Movement of the wedges 25 and 26 at right angles to
the separation o~ the base plate 11 ~rom the ram 12 is
controlled by a shaft 31 provided with oppositely directed
-threaded portions passing through threaded bores in the
wedges 25 and 26 so that rotation of the shaft 31 in one
direction will cause the wedges to move towards each other
and thus increase the separation of the base plate 11 from
the ram 12 and rotation of the shaft 31 in the opposite
direction will retract the ram 12 towards the base plate 11
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through the action of -the grooves 21 ancL 24 with -the
lugs on the wedges 25 and 26.
Along the upper edge of the dovetail-shaped grooves 21
and 24 -there is provided a gib or bearing s-trip 32 which
is secured by a number o~ adjusting screws 33 provided
with locking mlts 34.
Ehd plates 35 are provided at each end of the base
plate 11 and formed with bearing housings 36 for supporting
-the shaft ~1 for rotation. The ends of the ram 12 slide
between the facing surfaces of the end plates 35. The
housings 36 are provided with a flat portion 37 marked with
an index mark ~or use with a vernier indicator, which
indicates the separation of the ram 12 from -the base plate
11 from the rota-tion of the shaft 31.
The fixed member 13 is provided by a support cas-ting
having three bores 41 -to receive fixing bolts. The centre
bore is formed directly in the casting, but the two outer
bores are formed eccentrically in plugs 42 received in
larger bores 43 in the casting. Locking screws may be
screwed into -threaded apertures 44 in the cas-ting to secure
the plugs 42 in their desired position. Rotation of the
plugs in opposite directions will cause the member 1~ to be
inclined to the line of -the fixing bolts, and movement of
the plugs in the opposite directions allows the bolts to be
arranged in a triangle. Base plate 11 is provided ~ith
threaded bores 45 for securing the base plate 11 to the
fixed member 13.
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The fixed member 13 may be secured in a con~entional
mode to the bed of a machine -tool, which bed has an under-
side recess wi-th slo-ts extending from the bed face to the
recess. The slots are dimensioned to receive the shanks
of securing bolts which pass through the bores 41 and are
enlarged at one end for insertion of the securing bolt
heads Securing nuts are screwed onto the ends of the
bolts which protrude from the top of the bores 41 -to hold
the fixed member 13 securely on the bed of the machine
tool. Fixed member 13 is cast with rearwardly extending
webs 46 for s-trength.
The posi-tioning of the ram 12 relative to the base
plate 11 can be achieved in a variety of ways using the
sliding wedges 25, 26. ~The inclined faces can be between
the base plate 11 and the wedges instead of or~as well as
between the ram 12 and the wedges, as illustrated. When
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both sides of the wedges are inclined, the inclinations are
of course at different angles.
The illustrated arrangement of the wedges with their
narrower ends facing each other puts the shaft ~1 under
tension when the~wedge assembly is being expanded, but the
reverse arrangement (w1th~the wider ends of the wedges faclng)
may be used.
In place~of a shaft with oppositely-handed threads for
the two wedges, it is possible -to form the shaft with three
differently pitched threaded sectlons all of the same sense,
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the threaded section of intermediate pitch co-operating: .
with a bearing on the base or ram or end plates, and the
extreme threaded sections co-operating with respective
wedges. I~ the intervals between the pitches are equal,
there will be an equal and opposite movement of the wedges :~
relative to the component co-operating with the section of
intermediate pitch on rotation of the shaft.
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