Die set with two-part leader pins

Abstract

Disclosed herein is a die set in which the punch holder is guided for reciprocating movement towards and away from the die shoe by two-part leader pins, with the upper leader pin portions fixed to the punch holder and the lower leader pin portions fixed to the die shoe. Tapered surfaces on the upper leader pin portions are received in tapered sleeves on the lower leader pin portions to guide the movement of the punch holder. The tight fit of the tapered surfaces minimizes deflection of the punch holder to provide more accurate punching. Provision is also made for selecting the depth of stroke of the punch holder, and thus the punch, by utilizing a boss or stop on the end of the upper leader pin portion, which stop engages an abutment on the lower leader pin portion. The boss can be ground to the selected length to provide the desired travel of the punch holder and punch with respect to the work material and female die portion.

Description

SUMMARY OF THE INVENTION

The invention provides a die set which employs two-part leader pins for guiding reciprocal movement of the punch holder with respect to the die shoe and for controlling the length of travel of the punch holder towards the die shoe. Tapered male and female surfaces on adjacent ends of the two-part leader pins provide for a precise positioning of the male die or punch with respect to the female die with minimal deflection when the work material is engaged. The tapered surfaces are adjusted so that they are in shear when the punch is engaged with the work material so that there is no lateral deflection or translatory displacement of the punch for more accurate work than with a conventional die set.

Means are provided for adjusting the fit of the tapered surfaces and for adjusting the depth of penetration for precise control of the punch. This is particularly desirable when punching thin stock such as with a lamination die for transformer plates. With the die set of the invention the punch can be controlled so that the punch does not enter the female die, which results in a longer life for the punch.

Further objects, advantages and features of the invention will become apparent from the following disclosure.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a die set embodying the invention in fragmentary section and showing the punch and punch holder in retracted and advanced position.

FIG. 2 is a sectional view in reduced scale along line 2--2 of FIG. 1.

FIG. 3 is a fragmentary sectional view of a modified embodiment of the invention.

FIG. 4 is a fragmentary sectional view of a further modified embodiment of the invention.

DETAILED DESCRIPTION

Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other structure. The scope of the invention is defined in the claims appended hereto.

The die set conventionally includes a punch holder 10 connected to a mounting lug 12, and a die shoe 14. The punch holder 10 carries a punch or male die member 16, and a female die 18 is supported on the die shoe 14. In accordance with the invention there are provided upper leader pin portions 20 which can have a tapered shank 22 and be in a press fit in apertures 24 in the punch holder 10. The leader pin portions 20 are also provided with a tapered surface 26 which can be a continuation of tapered surface 22.

The leader pins 20 can also include an adjustment boss or stop 28 which projects axially form the lower surface 30 of the tapered portion 26. The purpose of the adjustment boss 28 will be hereinafter described in detail.

The lower leader pin portions 32 can have tapered surfaces 34 received in tapered apertures 36 in the die shoe. Projecting above the die shoe is a lower leader pin shank portion 38. Shank portion 38 is connected to a sleeve 40 which is provided with an internal tapered surface 42 complementary to the tapered surface 26. Means are provided for adjustably securing the sleeve 40 to the lower leader pin portion 32. In the construction disclosed in FIG. 1, the means comprises set screws 44. The set screws 44 enable adjustment of the position of the sleeve 40 relative to the die 18 or material to be punched 39 so that the tapered surfaces are in tight engagment or in shear at a point during penetration of the work material which enables separation of the punched blank from the work material 39 with no deflection of the punch.

In use of the die set thus described, the adjustment boss or stop 28 constitutes an adjustable stop which limits downward movement of the punch as it engages the top 41 of the lower leader pin portion 38. The user of the die set can thus grind the stop 28 to the desired depth to control travel of the punch and the depth of penetration of the punch into the female die 18. The adjustment of sleeve 40 is also taken into consideration when adjusting the stop 28. Although a stop 28 is shown in FIG. 1, if the die set and thus the leader pins are quite small, the stop 28 can be eliminated and the surface 30 of the upper leader pin portion can be ground to the correct length. The surface 30 and surface 41 will limit travel of the punch holder to the selected distance.

FIG. 3 shows a modified embodiment of the invention in which the upper leader pin portion 50 is provided with a threaded bore 52 which receives a set screw 54 which is adjusted to set the travel of the punch holder and punch.

FIG. 4 shows a further embodiment in which the upper leader pin portion 60 is provided with circumferential oil grooves 62 intersected by axially-extending oil grooves 64. The adjacent ends 66, 68 of the upper and lower leader pins can be provided with bores 70, 72 to serve as oil reservoirs for lubricating oil 78. The reciprocating movement of the upper leader pin portion 60 in sleeve 76 provides a pumping action to force oil between the ends 66 and 68 into the grooves 62, 64. The lubricating arrangement as thus described considerably lengthens the intervals for oil replacement which minimizes scoring and wearing problems which exist with conventional die sets.

As shown in FIG. 1, the mounting lug 12 for the punch holder is desirably provided with a tapered shank portion 80 which fits in a tapered opening 82 in the punch holder. The lug 12 is thus secured against withdrawal or severance from the punch holder 10 during upward movement of the punch holder 10.

The upper and lower leader pin portions are also provided with tapered surfaces to prevent withdrawal. The tapered surfaces 22 and 36 on the leader pins prevent separation of the leader pins from the punch holder and die shoe during use. The ram prevents withdrawal of the pin portions 20 from the punch holder during downward movement of the punch holder and the bolster plate 84 prevents withdrawal of the lower pin portions 32.

The tapered surfaces 26, 42 of the upper leader pin portion 20 and the sleeve 40 desirably have a taper of about 0.003 inches per inch although the taper is more pronounced in the drawings.

The use of two-part leader pins with tapered guiding surfaces and abutting ends enables control of the punch so that no penetration of the female die occurs. Thus wear of the male and female die is reduced to a minimum. In the event wear of the punch does occur and the punch is ground, the boss 28 or the end of the upper leader pin portion is also ground to maintain the travel of the punch at the selected distance.

Claims

What is claimed is:

1. In a die set including a punch holder and a die shoe, the improvement comprising an upper leader pin portion mounted on said punch holder and having a tapered surface decreasing in diameter remote from said punch holder, a lower leader pin portion anchored in said die shoe and having a tapered bore complementary to said tapered surface of said leader pin and adapted to telescopically and reciprocally receive said upper leader pin tapered portion and guide said punch holder during reciprocal movement of said punch holder and leader pin toward and away from said die shoe.

2. In a die set including a punch holder and a die shoe, the improvement comprising an upper leader pin portion mounted on said punch holder and having a tapered surface decreasing in diameter remote from said punch holder, a lower leader pin portion connected to said die shoe and having a tapered bore adapted to receive said upper leader pin tapered portion and guide said punch holder during reciprocal movement of said punch holder toward and away from said die shoe and wherein said bore is formed by a sleeve separable from said lower leader pin portion, and said sleeve has a bore for receiving said upper pin portion, and means for adjustably connecting said sleeve on said lower pin portion.

3. In a die set including a punch holder and a die shoe, the improvement comprising an upper leader pin portion mounted on said punch holder and having a tapered surface decreasing in diameter remote from said punch holder, a lower leader pin portion connected to said die shoe and having a tapered bore adapted to receive said upper leader pin tapered portion and guide said punch holder during reciprocal movement of said punch holder toward and away from said die shoe and wherein said upper leader pin portion has an adjustable stop and wherein said lower leader pin portion has an abutment portion engageable with said stop to limit travel of said punch holder.

4. The improvement of claim 3 wherein said stop comprises a projecting boss extending axially of said upper leader pin portion, the boss having a diameter less than said leader pin.

5. The improvement of claim 2 wherein said tapered surfaces of said upper and lower leader pin portions have a slope such that said surfaces mate at a pre-selected point in the travel of the punch to prevent deflection of the punch.

6. The improvement of claim 2 wherein said upper leader pin portion has intersecting axially and circumferentially extending oil grooves and including an oil reservoir in said lower leader pin portion.

7. The improvement of claim 3 wherein said adjustable stop comprises a threaded bore in said upper leader pin portion and a screw threadably received in said bore and adapted to engage said lower leader pin portion.

8. A die set in accordance with claim 2 wherein said punch holder has a tapered opening for receiving tapered surfaces on said upper leader pin portions with the tapered openings increasing in diameter toward the punch holder surface remote from the die shoe.

9. A die set having a punch holder and die shoe, the improvement comprising a mounting lug on said punch holder connectable with a ram, said mounting lug including a tapered shank portion and an aperture in said punch holder having a tapered surface for receiving said tapered lug surface, said aperture having its largest diameter at the punch holder surface adjacent the die shoe.