CA2098235A1 - Tooling for turret punch press - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An improved punch assembly tooling for turret punch presses is described. The tooling comprises removeable punch inserts which are connected to the striker assembly by a single retainer bolt located in a central bore running along the longitudinal axis of the punch assembly. This direct connection means of the components of the striker assembly improves tonnage transmission as impacts are not transmitted via springs, threads, pins or other intermediate links in impact path. Improvements in alignment and orientation are also provided as well as more reliable stripping. Inserts are simply removed from the front without having to remove entire punch assembly from turret bore.
The tooling also provides significant improvements in general ease of operation, reduced cost for punch inserts, and improved reliability due to sealed construction allowing more effective lubrication.

Description

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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

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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.

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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 .

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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.

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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 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.

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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 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.

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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~

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A tool assembly for a turret punch press, comprising a guide body positionable within a turret punch bore for 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 element extending downwardly therefrom and having a horizontal abutment surface abutting a corresponding abutment surface on said striker bar; and drawing means for pulling said punch insert upwardly 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.

2. A tool assembly as recited in claim 1, where said striker bar has an aperture therethrough about a central vertical axis, and where said drawing means comprises a bolt passing through said aperture in said striker bar and engaging threads in a central vertical hole in said punch insert.

3. A tool assembly as recited in claim 1, further comprising a striker head positioned above said striker bar, and drawing means for pulling said striker head and said striker bar together to force abutment surfaces on said striker head and striker bar into direct, solid contact with each other, whereby punching force is transmitted directly from said striker head to said striker bar and thence to said punch insert across said abutment surfaces.