Note: Descriptions are shown in the official language in which they were submitted.
~g~23~
Title: TOOLING FOR TU~RET PUN~I PRESS
5 Inventors: Salomon Maurice Fargeon, RolE W. Hoffman
Assignee: A Maurice and Sam Corp~, operating as AMS
Industries
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to tooling for turret punch presses,
and in particular to punches and dies for use with CNC turret punch
presses.
Description of the Prior Art
Turret-type machine tool metal worXing punch presses have
been in use for many years and have enjoyed significant commercial
success because they dramatically reduce the punching time in cases
2D where multiple punching operations are performed on a single
workpiece. With the advent of numerical controls for these turret
punch presses, the total workpiece punching time has been decreased
significantly further.
In many turret-type punch presses, the tool pair, i.e., the
punch and the die, frequently include a punch guide mounted for
209823~
limited reciprocal motion within the turret and biased into the turret
by a coil compression spring. This guide serves to: (a) clamp the
workpiece down against the die which is mounted in the turret under
the workpiece; (b) guide the punch itself which is reciprocally
mounted in the guide, and (c) strip the punch from the material as the
punch withdraws from the workpiece into the forward end of the guide.
I'ypically, the punch has an elongated cylindrical body
having a reduced inner end that threadedly receives a spring seat for
a coil compression stripper spring that biases the punch away from the
work into the guide. The forward end of the punch is also reduced and
defines the metal cutting shearing surfaces, and the shape of this end
of the punch, while sometimes merely circular, frequently has a non-
circular configuration of practically any shape desired.
There are two general types of standard tooling for common
types of turret punch presses~ In particular, the two most common
types of tooling for the popular l 1/4" size tooling station are
called standard tooling and standard drop-in tooling.
The prominent feature of standard tooling is that the punch
is provided in the shape of a rod which runs the entire length of the
complete tool assem~ly. The design presents problems when the punch
must be replaced or resharpened due to wear or breakage. The process
to remove the punch from the guide assembly is time consuming and
2~9~
involves the following steps: Firstly, the set screw in the punch
head is loosened with an allen key permitting the punch head to be
unscrewed from the punch. Secondly, the spring is removed from the
tool assembly, following which the punch can then be pulled out of the
guide. Reloading the punch after replacement or sharpening involves
the same steps in reverse.
Punch orientation is also less than satisfactory in the
standard tooling. Most often a small pin is inserted into the punch
perpendicular to its axis. The pin reciprocates within a
corresponding key way machined into the punch guide. This provides
a comparably small contact surface between the pin and the key way as
a means to provide orientation throughout the punching strok~. Over
time, this small contact surface wears down reducing the effectiveness
of the guiding action.
Other problems exist with standard tooling including the
requirement that the entire punch assembly be r~moved from the turret
to be lubricated, and additionally that tonnage transmission is low
as striking forces are transmitted through the threads of the punch
or striker head and the main punch body. Finally, the open body
construction of standard tooling often leads to contamination by dirt
and punch filings, thereby adding to the time and cost required to
maintain the units.
~5
~()9~35
The second main type of tooliny for modern turret punch
presses is called standard "drop-in" tooling. In this type of tooling
a similar punch is used to that in standard tooling. There are some
differences such as closet body construction and the use of multiple
springs, but the use of a similar punch means many of the same
disadvantages as in standard tooling have been noted with this type
of tooling.
Punches in these prior designs are completely machined parts
including a central guide portion with ~rusto-conical transitions on
both ends, a reduced inner stem portion, with threads at the proximal
end. For this reason the punches are quite costly and because
replacement is frequent, this adds signi~icantly to the resulting part
cost. Furthermore, the punches are usually hardened by heat treating,
and the rather large size o~ the punches results in a su~stantial heat
treating cost even though only the tip of the punch requires heat
tre~ ing.
In the past, there have been attempts to construct punches
in two pieces, that is, a holder and a separate punching element held
by a holder, but these attempts hav~ either resulted in a more costly
punching assPmbly or an unreliable assembly, or one in which the
punching element is not easily replaceable.
20~23~
In United States Patent No. 4,862,782 (Ernst), a 2 piece
turret punch press tool assembly i5 shown in which a punch insert i5
insertable from the front of the holder and held in position by a pin.
Separate guiding is provided for the holder on the punching element.
~hile solving the problem of thle large expense of punches (by
requiring only a smaller punch insert), the use of a small pin as the
sole means to secure the punc:h insert axially is somewhat
unsatisfactory. This system results in reliability problems and the
inability to "shim" the punch insert after sharpening. It also
results in reduced tonnage transmission and the necessity to "tap out"
the pin when the punch insert must be replaced.
It is a primary object of the present invention to provide
improved tooling for turret punch presses that ameliorates the
problems noted in the prior art.
~U~ARY OF THE INV~NTION
It is an object of the invention to provide a generally
improved punch and die for use on turret punch presses.
It is a further object of the invention to provide improved
tooling for turret punch presses that permits quick and simple
changing of the punch insert without removing the entire assembly from
th t t
e urre .
209g23~
It i.s yet a further object o~ the invention to provide
improved tooling for turret punch presses that is compatible with the
most common types of turret punch presses, being the thick and thin
turret types.
It is still a further object of the invention to provide
improved tooling for turret punch presses that permits a punch insert
to be shimmed after sharpeniny, to provide proper depth adjustment.
It is still a further object of the invention to provide
improved tooling for turret punch presses that provides superior
tonnage transmission from striking means to worksheet.
Thus, in the pr~sent invention improved tooling for turret
punch presses is provided, consisting of a punch comprising a guide
body positionable within a turret punch bore ~or down and up movement
therein towards and away from a workpiece and a die beneath said
workpiece, and a striking assembly moveable up and down within said
guide bore, said striking assembly comprising:
a striker bar;
a punch insert positioned beneath said striker bar, having
a punch 21ement extendîng downwardly therPfrom and having a horizontal
abutment surface abutting a corresponding abutment surface on said
striker bar; and
2~922~
drawing means for pulling said punch insert upwarclly against
said striker bar to force said abutment surfaces into direct, solid
contact with each other, whereby punching force is transmitted
directly from said striker bar to said punch insert across said
abutment surfaces.
Further features of the invention will be described or will
become apparent in the course of the following detailed description.
BRIEF DESCRIPTION OF q~IE D~AWINGS
In order that the invention may be more clearly understood,
the preferred embodiment thereof will now be described in detail by
way of example, with reference to the accompanying drawings, in which:
Fig. 1 is a cross-sectional view of one preferred embodiment
- of the present invention for use with thick turret type presses.
Fig. 2 is a cross-sectional view of another preferred
embodiment of the present invention for use with thin turret type
presses.
Fig. 3 is an exploded view of the main components of the
tooling of the present invention.
Fig. 4 is a bottom view of the guide body showing the slots
to receive the pins on the stripper insertO
FigO 5 i5 a side view of the stripper insert.
209~23~
DETAILED DESCRIPTION OF 'rHE PREFERRED EMBODIMENT
Referring to Fig. 1, there is provided one embodiment of an
entire punch assembly 1 and corresponding die 26 of the present
invention. The punch assembly 1 has a generally cylindrically
elongated shape being defined by a main guide body 8 and a guide body
retainer cap 6 threadedly attached to said guide body with thread~ 7.
The guide body 8 is seen to have an internal stepped bore 21 that
receives and encloses the striker assembly and the stripping spring
2.
In this embodiment the striker assembly comprises four main
components: a punch insert 18, a striker bar 12, a connecting or
drawing means 10 between the punch insert 18 and the striker bar 12,
and finally the striker head 4. Alternati~e embodim nts could
include a striker assembly wherein the striker head and the striker
bar are one piece. The punch insert 18 forms the distal or lower end
of the striker assembly, being the snd closest to the die 26. The
punch insert 18 is releasably attached to the striker bar 12 via the
connection means lO. The tip o~ the punch insert 18 is the punching
element that comes in direct contact with the workpiece.
In the pre~erred embodiment, the connection or drawing means
10 used between the punch insert 18 and the striker bar 12 is a
retainer bolt 10 which is located in a longitudinal axial stepped bore
2~9~23~
13 running through the striker bar 12 and in a similar bore located
in the top portion of the punch insert 18. The retainer bolt 10 is
provided with threads at its lower end which reciprocate with similar
thraads found in the punch insert 18. The retainer bolt is typically
provided with an Allen key fitting on its upper transverse surface.
A lock washer 9 is employed between the retainer bolt 10 and the
striker bar 12 to prevent loosening of the striker assembly during
operation. An alternative drawing means could include threads on the
striker bar which directly directly reciprocate with threads on the
punch insert 18.
When attaching the punch insert to the striker bar 12, the
retainer bolt 10 is tightened until the upper surface of the insert
abuts the lower surface of the striker bar. This provides a larger
surface area over which the turret's striker force is distributed,
improving tonnage transmission and avoiding the unreliability of
designs where the striki.ng force i~ transmitted through threads,
springs, pins or the like.
The proximal end of the striker assembly consists of the
striker head 4 which provides the upper surface for the entire punch
assembly 1 to come in contact with the .impacting unit of a turret
punch press (not shown). The lower portion o f the striker head 4
extends partway into the central bore of the striker bar. The lower
portion of the striker head 4 and the upper portion of the striker bar
2~9~23~
bore are provided with reciprocating threads which form the releasable
attachment means between these two components of the striker assembly.
The striker head 4 is also provided with a lower flange that sits on
top of the upper transverse surface of the striker bar 12. When the
two components are threaded together they are tightened until this
flange meets the upper surface of the striker bar 12 so that the
threads do not bear the force of the impacting unit from the turret
punch press.
The striker head 4 also contains an axial loniytudinal bore
to permit access to the retainer bolt 10 when the bolt needs to be
loosened to change a punch insert 18.
This method of retaining the punch insert 18 is significant
in that it allows inserts 18 to be shimmed for proper depth adjustment
once they are sharpenedO This feature is not present in prior art
systems and can dramatically lengthen the useable life of inserts 18,
thereby reducing system costs.
The generally annular guide body 8 is mounted for limited
reciprocation within the turret bore (not shown). The body 8 is seen
to include an external step llb which cooperates with a similiar step
located in the internal turret bore (not shown) of most commercial CNC
turret punch presses. This step forms part of the locating and
securing means used to hold the guide assemhly 1 in the turret bore.
209~233
The guide body 8 thus comprises a laryer diameter upper
annular section and a somewhat smaller diameter lower annular section.
At the distal end (die end) of the lower section 8 there is provided
an aperture 25 into which i5 inserted a stri.pper insert 24. The
stripper insert 24 is also generally annular in shape having a central
aperture 27 which is shaped to correspond with the the shape of a
particular punch insert 18. The stripper insert 24 is releasably
attached to ths lower end of the guide body 8 with snap in pins 23
located on the insert which are received into slots 29 in the lower
transverse surface of the guide body. The pins 23 are retained in the
slots by fricition fit although other suitable retention means could
be used. Alternativley, snap-in grooves which are similar are
sometimes used in thick wall turrets due to increased resiliency of
turret si.de walls.
- The guide body 8 has an internal guide bore 21 that
guidingly receives the striker assembly and the stripping spring 2,
as described above. Thus, the guide body provides guiding for the
striker assembly as it moves inside the guide bore 21. As the four
com~onents of the striking assembly form a single rigid unit, which
unit includes the punch insert 18, no separate guiding mechanism is
provided or re~uired for the punch insert 18.
In operation, the striker assembly is urg d toward the
retracted position inside the guide body 8 by stripping spring 2. As
11
209~23~
the striker head ~ is impacted by the striking means in the press, the
entire striking assembly moves downwards wi-thin the guide body 8 until
the lower surface of the guide body 8 contacts the worksheet (not
shown) and clamps it against the upper surface of die 26, and
thereafter the striker assembly continues its downward movement with
the insert sliding through aperture in the stripper insert 24 punching
worksheet and driving through the die 26. Thereafter, stripping
spring 2 acts to pull the striker assembly, including punch insert 18
back through the worksheet and into the guide body 8 with a stripping
action and the spring 2 moves striker assembly back to its FIG~ 1
position.
Orientation .in Thick Turret Systems
Orientation is effected in different manners with respect
to standard khin and standard thick turret systems. In thick turret
systems as shown in FIG. 1, the punch insert 18 is angularly fixed
with respect to the guide body 8 by an orientation pin 15 permanently
mounted in a chordal bore in guide body 8. The orientation pin 15
engages the flat upper surface 17 of the punch insert 18 thereby
ensuring proper orientation between the insert and the guide body.
Angular orientation of the other components in the striker assembly
is not necessary.
""~ , , " ,,", " ", ", ,,~" ~;,, ~, "
20~23~
Orientation between the guide body 8 and the turret is
effected via orientation slots 19 found in the outerwall wall of the
lower portion of the ~uide body. These slots 19 receive corresponding
keys located in the turret bore thus ensuring correct rotational
orientation, and preventing relative angular movement between the
guide body or the punch insert 18 with respect to the turret. At the
same time the length of the slot 19 and the flat 17 permits the punch
insert 18 to move vertically relative to the guide body 8 and also
permits the guide body to move vertically relative to the turret.
Punch insert 18 also has a slug ejector for assembly 1
mounted therein including a spring 20 biased slug ejector pin 22.
This system avoids avoids exposure of the insert (or punch)
18 often found in systems using "open'l keyways for orientation. In
these prior art systems the outer section of the orientation slot is
used to orient the guide body to the turret, while the inner portion
of the keyway is used to orient the punch (insert) to the guide body.
This results in an open keyway to the inner portion of the punch that
can allow metal filings etc. to enter causing reliability problems.
Variations in Orientation for Thin Turret Systems
In the FIG. 2 embodiment a somewhat different punch assembly
~5 is illustrated that is substantially the same as the punch assembly
13
2~23.~
illustrated in FI~. 1 except that assembly is configured somewhat
dif~erently to accomodate the dimensions found in standard thin turret
systems. The main difference is in the structure provided for
orientation, otherwise, the principles of operation and construction
are the same in both.
The punch assembly o~ FIG. 2 is again seen to include a two-
piece guide body, housing a striker assembly including a punch insert,
and a stripper spring assembly 2 for retxacting the striker assembly
into the guide body 8.
The punch tip insert 18 is again onstructed of a hardened
steel or carbide alloy and includes an upper enlarged cylindrical body
portion having a flat chordal surface again termed an orientation flat
17 that engages a complementary flat surface on the two way
orientation key 17b to rotationally lock the punch insert 18 with
respect to the guide body 8~ This rotational locking is essential for
all non-circular punch insert tip which require accurate angular
orientation for proper punching.
Orientation key 17b however, provides a double function as
it extends through guide body wall and into a reciprocating keyway in
turret bore to also provide rotational locking between guide body and
turret. Top of key 17b extends behind striker bar 12 80 as to retain
key in place when punch insert 18 is removed ~or some reason.
1~
2~9~23~
Punch insert 18 again also has a slug ejector for assembly
1 mounted therein including a spring biased slug ejector pin 22.
An important aspect of the present invention is that the
retainer bolt 10 is accessible through the central opening in the
striker head 4. This permits the punch insert 18 to be removed, if
desired for sharpening or replacement or to change shapes, after the
punch assembly 1 has already been installed in the turret. The
operator simply has to insert the appropriate tool through the central
opening and loosen the retainer bolt. ~here is no need to remove the
entire punch assembly 1 or to tap out a locking pin, thereby
facilitating rapid and simple insert 18 replacement~
