Improvements in Presses for Drawing Through and Forming Up Sheet Metals.
Year: 1891

page_text: Date of Application, 7th Mar., 1891
Complete Specification Left, 5th Dec., 1891-Accepted, 16th Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in Presses for Drawing Through and Forming Up
Sheet Metals.
I, WINGFIELD BURTON of Market Street Bilston, in the County of Stafford,
Mechanic, do hereby declare the nature of this invention to be as follows:-
Instead of as formaly useing cams & rollers for lifting & lowering the pressure
plate or blank holder, I use two or more knee levers. The "levers" are for the
purpose of moveing the pressure plate or blank holder up & down. The lower part of
the centre peice or plunger having progections which engage with rollers fixed upon
the levers (by means of spindles through the same) and so lift the pressure plate or
blank holder off the die.
And what I claim is. An improved method of moveing the pressure plate or
blank holder to a greater height from the die, & also holding the pressure plate
when down without strain upon the crankshaft & with greater accuracy
& with greatly increased pressure than can be obtained with cams & rollers as
now used.
Dated this 6th day of March 1901
WINGFIELD BURTON.
COMPLETE SPECIFICATION.
Improvements in Presses for Drawing Through and Forming Up
Sheet Metals.
I, WINGFIELD BURTON, of Market Street, Bilston in the County of Stafford,
Mechanic, do hereby declare the nature of this invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
In presses for the purpose mentioned in the title, the sheet metal to be operated
upon is held between the top of the bottom die and a pressure plate or blank
holder, while the plunger or upper tool is brought down through an opening in the
pressure plate and in the moving block which carries it and forces the sheet metal
into the bottom die, the metal which is pressed between the pressure plate and top
of the bottom die being drawn inwards by the operation of the punch. The purpose
of the pressure plate is, as is well known, to prevent the metal puckering. The
means heretofore adopted for putting, and maintaining for the required time, the
necessary pressure on the pressure plate, have been unsatisfactory, as involving
a considerable and sometimes an enormous amount of friction (throwing, when the
plate is operated by cams on a crank shaft which works the plunger, a heavy strain
on such shaft), besides not conveniently admitting of the raising of the plate as
high as is desirable for readily putting a blank in place, and lifting it, when formed
up, out of the bottom die when requiring to be removed therefrom in such manner.
According to the usual method also of operating the pressure plate, the heavy
strain causes great wear of the friction rollers and interferes with the accurate
bedding of the plate.
Now, this invention has for its object improved means of putting and maintaining
the pressure on the pressure plate, and of raising it on the return of the punch,
whereby, while a greatly increased pressure may be ensured, friction is very con-
siderably reduced in putting on the pressure, and is practically avoided and the
shaft (when such is used for operating the plate) relieved of strain while the
pressure is maintained, thus reducing to a minimum the wear of the parts by which

page_text: the operation of the plate is effected and ensuring greater accuracy in the bedding
of the plate upon a blank; and whereby the plate is conveniently raised to a
greater height than heretofore, affording consequently increased facility in putting
in the blanks, and removing them upwards from the bottom die, when required to
be so removed, after they have been formed up.
The above object is effected, according to this invention:-by suspending the
moving block which carries the pressure plate from the framing of the press by
means of knee levers or arms, that is to say, levers or arms formed each in two
lengths pivoted together and their extremities pivoted the one to the framing and
the other to the moving block which carries the pressure plate; by providing each
such lever or arm with a roller, (projection or corresponding part), and providing
the moving head (which carries the punch) with tappet pieces or lifters which, as
the head rises, lift the rollers (projections or corresponding parts) and so draw the
knee levers or arms out of line into an angular form and raise the plate; and by
forming vertical surfaces or slides on the moving head terminating in shoulders at
the bottom, of which the shoulders put on the necessary pressure by forcing out the
rollers (projections or corresponding parts) to bring the knee levers or arms each
into a straight position, and of which the vertical portions maintain such pressure
by ensuring against the rollers (projections or corresponding parts) moving inwards
during the operation of the punch upon the sheet metal. As the rollers are being
raised they move inwards below the shoulders aforesaid. Each roller (projection or
corresponding part) is, preferably, placed, for the purpose of giving increased lift of
the plate, intermediately between the pivoted connection of the two lengths of lever,
forming a knee lever, and the point of suspension, and the nearer it is placed to
the latter the greater of course will be the lift; but in fixing the exact position
regard must be had to the fact that the upper side of the moving block carrying the
plate must not, in working, foul the underside of the moving head.
As a practical illustration of the above described invention, I will proceed to
describe it with reference to the accompanying drawings, of which
Figure 1 is a front elevation of a press with my invention applied thereto;
Figure 2 is vertical section taken on line x x of Figure 1, with the crank
shaft, connecting rod, and moving head, removed, for convenience of illustration ;
and
Figure 3 is a section taken on line y y of Figure 1.
In these illustrations the tools, that is to say, the punch, bottom die, and pressure
plate, are omitted as they vary in shape and size according to the work to
be done.
The press illustrated is (except for the application of my improvements thereto)
of the common type in which an overhead crank shaft A, carried in bearings in the
framing B, imparts through the medium of a connecting-rod C, vertical movement
to a moving head D guided in guides formed with or fixed to the framing. The
block E, however, which carries the pressure plate is suspended by four knee levers
or arms a b, of which the portions ab are pivoted together at c, and of which the
upper extremities are pivoted to the framing at d and the lower extremities are
pivoted to the block E at f. Rollers g are carried to turn on pins / fixed to the
levers or arms preferably, as shewn, in position intermediate between the pivot
centres c and d. The pins at the front of the press are connected, respectively,
(so as the better to support the rollers) with the corresponding pins at the back,
by bars i formed each in one length with the opposite pins on the same side of the
press. The parts marked g', Figure 2, are merely reduced portions of the rollers g
to give increased length of bearing and fill in the space between the rollers and
arms a. Tappets or lifters j are formed on the moving head D in position, as
shewn, to catch and raise the rollers as the head is litted, and thus draw inwards
the pivoted joints so as to move the arms a and of cach knee lever into an
angular position with one another and so raise the block E. The tappets j curve
upwards towards their outer ends, as shewn, to give an easy action in commencing
to lift the rollers. As the rollers are moved inwards they pass into the slotted
C

page_text: openings k in the head, such openings being formed to allow of the inward move-
ment of the bars i also. As the head descends again, the weight of the block E
and pressure plate which it carries tends to draw the knee levers back again into
their straight position, and would draw them completely into such position but for
the plate coming down upon the blank. When the blocks and plate cease to fall of
their own weight, shoulders l, forming the upper side of the slots k (or the outer
corners of such shoulders, and which are preferably slightly rounded) press against
the rollers and force them outwards until the knee levers are each brought into line
and the plate thus pressed so tightly on to the blank as to flatten it down upon the
bottom die and hold it with great force or pressure. As the head D continues to
descend, vertical surfaces m of the head, pass down between the rollers and thus
maintain the knee levers in their vertical or straight position, against any tendency
to move inwards. A small force suffices to maintain the levers in their straight
position, and they are prevented from opening outwards from such position by
projections or stops n on the framing, or by other suitable means, such as knuckle
joints. An unyielding pressure is thus maintained on the plate with practically no
friction between the rollers and surfaces m.
The arms
a of the knee levers bed at their upper ends in recesses in the
framing, and at their lower ends in blocks o carried by the block E, and bed
at their middle joints one within the other, and thus the joint pins are relieved from
strain as the levers are moved into and retained in their straight positions.
In the illustrations four knee levers a bare shewn as are preferred for larger
presses. For smaller presses two of such levers only may be used, namely,
one on each side operating within spaces provided in the framing B B. Such
an arrangement of the knee levers a b, with the necessary modification of
the moving head D to adapt it thereto, will be readily understood without need
for further description.
The means by which the block E carrying the pressure plate is operated,
according to this invention, readily permits of the moving head being operated by
a bydraulic cylinder instead of by a crank shaft and connecting rod, such means of
operating the head being a great desideratum in presses for drawing through and
forming up sheet metals.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that
what I claim in respect of presses for drawing through and forming up sheet
metals, is :--
1. The means, substantially as described with reference to the drawings herewith,
by which pressure is put and maintained on the pressure plate, and the plate
subsequently raised.
2. The combination of a pressure plate, suspended by means of knee levers
or arms, with rollers (projections or corresponding parts) carried by such levers or
arms, and with tappet pieces or lifters carried by the moving head, which as
such head rises, engage with the rollers (projections or corresponding parts) and
move the levers or arms at their intermediate joints and thus raise the plate, and
with means by which as the head descends again portions carried thereby ensure the
proper return movement of the levers or arms and maintain them in position during
the operation of the punch, substantially as described.
3. The combination of a pressure plate, suspended by means of knee levers or
arms, with rollers (projections or corresponding parts) carried by such levers
or arms, against which portions carried by the moving head press to force the
knee levers or arms into a straight or approximately straight form, to put on
the pressure and maintain it during the operation of the punch, and with means
by which, as the head rises, the levers or arms are each moved at their intermediate
joints so as to bring them into angular form and thus raise the plate, substantially
as described.
4. A pressure plate suspended by means of knee levers or arms, in combination

page_text: with rollers (projections or corresponding parts) carried by the upper members of
such levers or arms in position intermediate between their end centres, and with
means by which such rollers (projections or corresponding parts) are lifted during
the upward movement of the punch, substantially as described, for the purpose
set forth.
T
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicant.