US3608650A

US3608650A - Impact cylinder apparatus

Info

Publication number: US3608650A
Application number: US877773A
Authority: US
Inventors: Saburo Matsusaka
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-11-30
Filing date: 1969-11-18
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28

Abstract

An impulse stamping device having a cylinder in which a hollow piston and piston rod are mounted. The piston rod extends outwardly of the cylinder and has mounted at its end a dieholder. A ram having a head at its upper end is mounted within the hollow rod. The head is adapted to seat within a second cylinder located axially at the upper end of the first cylinder. Compressed gas is fed selectively to the cylinders to operate the piston rod and ram in sequence to first lower the dieholder and thereafter ram the die against the workpiece.

Description

United States Patent IMPACT CYLINDER APPARATUS 5 Claims, 5 Drawing Figs.

US. Cl 173/114,

173/1 34,227/147 Int. Cl B2511 9/00 Field of Search 173/1 12,

Primary Examiner-James A. Leppink Attorney-Kurt Kelman ABSTRACT: An impulse stamping device having a cylinder in which a hollow piston and piston rod are mounted. The piston rod extends outwardly of the cylinder and has mounted at its end a dieholder. A ram having a head at its upper end is mounted within the hollow rod The head is adapted to seat within a second cylinder located axially at the upper end of the first cylinder. Compressed gas is fed selectively to the cylinders to operate the piston rod and ram in sequence to first lower the dieholder and thereafter ram the die against the workpiece.

PATENTEDSEP28I971 SHEET 1 [1F 2 Fig.7

AGEUT sum for 2 PATENTED'SEHB isn INVENTOR SABMlo MArsvsAuA MENF IMPACT CYLINDER APPARATUS BACKGROUND OF THE INVENTION The present invention relates to an impact stamping device and in particular to an improved device by which the die is first moved into position against the workpiece and is the rammed.

Generally speaking, the operation of stamping and rivet fastening apparatus by employing an impact impulse is most desirable, because the application of an impact force permits these apparatuses to be dimensioned smaller and lighter than those which work by the application of static stress and pressure.

However, when conventional impact cylinder apparatus for example, a marking machine, is employed, the impact piston jumps up due to the reaction of the impact of the die against the workpieces. This often results in two or more successive impulses, so that the article is displaced by the impact vibration and may often have duplicate stamp positions effected from the same letter or figure. Many of other conventional examples presented different defects such as the generation of back pressure on the piston during operation, thus decreasing the work efficiency.

It is the object of the invention to provide an improved apparatus, of simple structure and function overcoming the defects of the conventional devices and providing improved finished workpieces at high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of the apparatus of the invention, in

' the initial state of operation,

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings the apparatus of the present invention comprises, a cylinder 1 which has an upper head 2 and a lower head 3. A hollow piston 4 slides hermetically inside cylinder 1 and is integral with a hollow piston rod 5. A piston 7 is formed on the upper part of a ram 6 sliding hermetically inside both hollow piston 4 and hollow piston rod 5. A stamp holder 9 holding a stamp die 8 is slidably supported by the lower part of hollow piston rod 5. Hollow piston 4, lower head 3, hollow piston rod and piston 7 are respectively provided with respectively a packing 10, a gland packing l1, and packings l2 and 13. The upper head is internally cutout to form an air cavity 14 and a cylinder portion 15 above it. The piston 7 hermetically sealed with packing 13 slides inside the cylindrical portion 15. Orifices 16 are distributed in the periphery near at the bottom of hollow piston rod 5. An annular opening 17 is positioned in the bottom of hollow piston rod 5 and supports an upper portion 24 of the stamp holder 9. A lower portion 18 of stamp holder 9 has a hole 20 for holding a tool or die 8 by a Shank 19 which is inserted in the holder and supported by a set screw or bolt. The space within cylinder 1 surrounding the piston rod 5 under hollow piston 4 is defined a and the space within cylinder 1 between upper head 2 and hollow piston 4 is defined b.

Numerals

21 and 22 denote respectively four-way and three-way changeover valves, 23 a gaseous pressure source, 25, 26 and 27 gas ports for both inlet and outlet, 29 a velocity control valve, and 30 an article to be stamped, which is placed on a table 31.

The functions of stamping operation for the examples of FIGS. 1-3 will be explained.

In FIG. I, compressed gas is initially introduced to a space a inside cylinder 1 through port 27 applying a pressure on the bottom surface S of hollow piston 4, causing the hollow piston 4 to be pushed up into contact with the upper head 2 assuming the upper dead point piston 7 and ram 6 are carried by hollow piston 4 and supported with the piston sealed within the cylinder 15, whose orifice 26 is open to atmosphere.

When four-way valve 21 is changed over, compressed gas in said space a under hollow piston 4 is discharged through port 27 and new compressed gas through port 25 from the gaseous pressure source 23 is introduced into air cavity 14, and then hollow piston 4 starts descending as shown in FIG. 2. With regard to piston 7 and ram 6 which are movably supported relative to hollow piston 4; since cylindrical portion 15 is opened to the atmosphere through three-way changeover valve 22, a force F, generated by compressed gas introduced into air cavity l4 acts on piston 7 in an upward manner to support it at the upward end in the cylinder 15 as shown in FIG. 2. Therefore F 1 may be calculated as follows:

A cross section of piston 7 A cross section of ram 6 P, gas pressure inside air cavity 14 W: weight sum of ram 6 and piston 7 As the hollow piston 4 continues descending from the position of FIG. 2, the stamp 8 comes to contact with article 30 until the bottom face 37 of the hollow piston rod 5 presses against the upper surface 38 of the lower portion 18 of stamp holder 9 and impresses stamp 8 on article 30.

The three-way valve 22 is then changed over, and compressed gas is supplied through port 26 against the face of the piston 7 so that piston 7 and ram 6 themselves start descending. As piston 7 descends downward and passes out of cylindrical portion 15 reaching the air cavity 14, compressed gas introduced into the air cavity b formed above the hollow piston 4 by the descent of hollow piston 4 inside cylinder I simultaneously comes to act on piston 7 and ram 6 causing ram 6 to accelerate rapidly in the downward motion.

In this condition, as the diameter of hollow piston 4 is much larger than the diameter of ram 6, the air cavity b serves as a gas reservoir. Even if the quantity of compressed gas supplied to the air cavity b through

ports

25 and 26 is rather little, pres sure in the air cavity b does not substantially change and maintains a sufficiently high pressure during the high accelerative motion of ram 6.

If the downward force on ram 6 is denoted by F then F =A P -W wherein, P denotes the pressure inside the air cavity b on hollow piston 4 as shown in FIG. 3.

In this manner ram 6 being gradually accelerated by force F collides against the upper surface of stamp holder 9 as shown in FIG. 3. If the energy obtained in case of the collision is denoted by E, then E=F '-l wherein, [denotes the length of descent of ram 6 to its point of collision against stamp holder 9,

F '=A P '+W wherein, P denotes the mean pressure in the air cavity b during the descent of ram 6.

As a result of the colliding of ram 6 against stamp holder 9, article 30 is marked by stamp die 8, therefore, one cycle of stamping operation in the present invention is finished.

If

changeover valves

21 and 22 are returned to the state of FIG. 1, hollow piston 4 is pushed upward, and accordingly ram 6 is also lifted to restore the state of FIG. 1.

All the above descriptions concern a stamping operation rivet fastening employing the same apparatus is described with reference to FIGS. 4 and 5. In these drawings, a punch 32 for fastening rivets is suspended from the lower part of hollow piston rod 5. In FIG. 5, 33 denotes an anvil placed on the table of a press frame, 34 a rivet, 35 and 36 articles to be incorporated by the rivet.

When four-way valve 21 is changed over similarly to the case of stamping operation, hollow piston 4 and hollow piston rod 5 descend, and so bottom face 37 of hollow piston rod 5 pushes the articles against anvil 33 as shown in FIG. 5. At the same time punch 32 contacts with the rivet and is pushed upward.

Subsequently, when three-way valve 22 is changed over and ram 6 descends rapidly then the bottom end of ram 6 strikes the upper end of punch 32 to fasten rivet 34.

In the stamping operation, the present invention provides a preliminary pressing operation which can assure a clear finished workpiece without the least displacement between the stamp and articles, even if the ram should rebound and stamp repeatedly. Similar advantage will also be apparent in the rivet fastening operation. Rivet fastening is performed by the impact force of the ram only after pressing and contacting the die and articles together. Thus rivet fastening operation is performed excellently. Even if a rivet is inserted askew or on the tilt or in a rivet hole of surplus size, it will be corrected to its normal position by the preliminary contact and the part to be combined will be perfectly fastened. Furthermore, apparatus of smaller dimension will render large effective power so that oversized apparatus is not required.

As illustrated above, the present invention permits the hollow piston 4 and the hollow piston rod 5 to serve as a pressing mechanism in the stamping and the rivet fastening operation, and to lift piston 7 and ram 6 so that piston 7 may be inserted into cylindrical portion and supported. Hollow piston 4 is caused to descend downward by compressed gas introduced in air cavity 14 through port 25, and at the same time piston 7 and ram 6 are caused to be pushed upward and supported at upward end of cylindrical portion 15 by said compressed gas. After that, by operating changeover valve 22, compressed gas is supplied through port 26 to piston 7, causing piston 7 and ram 6 to descend downward. The compressed gas in the air cavities l4 and b cylinder 1 cause ram 6 to accelerate rapidly downward. As the air cavity inside cylinder 1 has a larger volume of sufiiciently, compressed gas the air cavities are maintained at a sufficiently high pressure during the accelerating motion of ram 6. The downward motion of ram 6 is not prevented by any back pressure because the piston rod 5 is opened to the atmosphere through orifices 16. Consequently the present invention provides apparatus of high efficiency capable of reduced manufacturing cost.

What is claimed is:

1. Impact apparatus comprising a cylinder having an upper and lower head defining therebetween a first air cavity, said upper head having a cutout portion defining a second air cavity, an axially hollow piston and integral piston rod, said hollow piston movably mounted within said first air cavity and dividing said cavity into upper and lower portions, said hollow piston rod extending through said lower head outwardly of said cylinder and having an opening at the end thereof, a die holder movably mounted in the opening of said hollow piston rod, a ram slidingly mounted within said hollow piston and piston rod, said ram extending between said die holder and the upper end of said hollow piston, a ram piston head integral with the upper end of said ram having a profile adapted for insertion into said second cavity, means for introducing a gas under pressure into said upper portion of said first cavity to act simultaneously on said hollow piston and said ram piston head, and means for introducing a gas under pressure to said second cavity to act on said ram piston head whereby said hollow piston and rod may be moved downwardly through said first cavity at a predetermined rate and said ram may be moved downwardly through said hollow piston rod at a second predetermined rate.

2. The apparatus according to claim 1 including means for accelerating said ram a speed greater than said piston rod.

3. The apparatus according to claim 1 wherein the ram piston head has a lower surface adapted to be carried by said hollow piston and wherein means are provided for introducing gas under pressure into the lower portion off said first cavity to lift said hollow piston and said ram piston head.

4. The apparatus according to claim 3 wherein each of said means for introducing air comprises selectively o erable valve means and means for operating said valves to o tam sequential movement of said piston rod and ram.

5. The apparatus according to claim 1 wherein said second air cavity comprises a cylinder adapted to receive said ram piston head in sealing engagement therewith, said ram piston head being adapted to move out of such engagement on introduction of gas under pressure to said second cavity and into said first cavity to be acted thereon by the introduction of gas under pressure thereto.

Claims

3. The apparatus according to claim 1 wherein the ram piston head has a lower surface adapted to be carried by said hollow piston and wherein means are provided for introducing gas under pressure into the lower portion of said first cavity to lift said hollow piston and said ram piston head.

4. The apparatus according to claim 3 wherein each of said means for introducing air comprises selectively operable valve means and means for operating said valves to obtain sequential movement of said piston rod and ram.