US2834234A - Coin dimpling apparatus - Google Patents

Description

May 13, 1958 H. R. FISCHER com DIMPLING, APPARATUS 2 Sheets-Sheet 1 Filed May 25. 1954 INVENTOR ion 4 90 A? Fad/5? ATTORNEY May 13, 1958 FISCHER 2,834,234

COIN DIMPLING APPARATUS Filed May 25, 1954 2 Sheets-Sheet 2 ATTORNEY United States Patent COIN DIMPLING APPARATUS Howard R. Fischer, Utica, N. Y., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application May 25, 1954, Serial No. 432,185

14 Claims. (Cl. 78-18) This invention relates to apparatus for the formation of dimples in metal sheets, particularly those made of high strength alloys commonly used in aircraft construction. Such dimples have a tendency to stretch and crack, and to overcome this difiiculty it has been proposed to coin or forge the metal within the dimple by employing a yielding ram supported in the dimpling die immediately surrounding the pre-formed hole or opening As the load is applied, the coining ram compresses and forges the sheet metal around the opening, preventing expansion of the opening and reducing the danger of development of cracks in the dimpled material.

In coin dimpling, correct application of force to the coining ram is an important and critical factor in the formation of sound, crack-free dimples. On conventional equipment for this purpose, this force is developed and applied by adjustable spring pressure. The useof a spring as the ram loading source, has the disadvantage of limited movement, spring variation, excessive gain of force during spring deflection and lack of a precise method of force adjustment. In some instances the post which supports the coining ram is collapsed and broken under the pressure of a dimple of excessive depth.

The general object of this invention is to control the pressure on the coining ram in such a manner as to form sharp radius, crack-free dimples of uniform quality.

Another object is the provision of a high initial coining force application without the consequent increase in force as the dimpling operation progresses. A further object is to increase the total available force on the coining ram. A still further object is to permit convenient adjustment of the loading force on the coining ram without requiring the use of tools. Still another object is to provide an exact and constantly visible indication of the amount of coining force being applied. Another object is to increase the range of movement of the coining ram against the yielding force. A further object is to permit sufiicient movement of the ram and post so that breakage thereof is prevented.

According to the present invention, the conventional spring pressure for holding the coining ram is replaced by air pressure under control of a pressure regulator. Air pressure is applied to the post for the coining ram in such a manner that the coining ram operates under a high initial pressure which remains substantially constant throughout the dimpling operation. In this way the forces which bend the sheet metal and the forces which coin the metal, or causes it to flow, operate simultaneously and are properly coordinated from the time that the dimpling operation first commences.

Other objects and features of this invention will appear more clearly from the description which follows.

In the accompanying drawings:

Fig. l is a longitudinal section of a portion of a dimpling machine embodying this invention.

Fig. 2 is a cross section as indicated by the arrows 2 in Fig. 1 showing the means for centralizing the dimpling punch.

' metal of different thickness.

2,834,234 Patented May 13, 1958 Fig. 3 is a fragmentary view on a larger scale showing 'the relation between the punch, die, coining ram and sheet metal at the completion of a coin dimpling operation.

Fig. 4 is an elevational view showing the pressure fluid supply line for the air cylinder, including a pressure gauge and indicator.

Figs. 5, 6 and 7 are enlarged views of fragmentary portions of Fig. 1; Fig. 5 showing the punch holder assembly, Fig. 6 the die and coining ram assembly, and Fig. 7 the bottom part of the air loaded post assembly.

Fig. 8 is an enlarged longitudinal section of the pressure regulator shown in Fig. 4.

Fig. 9 is an enlarged fragmentary section of the air cylinder showing the drain valve.

In the illustrative embodiment of the invention the dimpling machine comprises a massive yoke 11 having upper and lower jaws 12 and 13 respectively. Referring to Figs. 1 and 5, the upper jaw supports a plunger 14 for vertical reciprocation therein. Secured to the lower end of the plunger is a punch holder shank 15 having a central bore which loosely receives the upperend of a punch holder 17. As shown in Fig. 2the shank has four radially extending set screws 18 engaging the outside of the punch holder near the upper end of the latter whereby the axis of the punch holder may be adjusted to assure that it is in proper alignment with a dimpling die 19. The shank 17 also has four vertical threaded openings to receive bolts 20 which support the punch holder 17. The punch holder has enlarged holes to receive the bolts 29 and therefore is permitted to move transversely in response to the adjustment of the screws 18. The punch holder 17 is bored to provide a socket for the upper portion of a dimpling punch 21, whose lower portion is adapted to cooperate with the dimpling die 19. Any suitable means,'such as a resilient ring 22 and a locking screw 23, may serve to retain the punch in assembled relation in the holder 17 with the punch seated against the lower end of the holder. The lower extremity of the punch 21 has the usual projection 24 which extends into the hole in the sheet 25 being dimpled, as shown in Fig. 3.

The stationary dimpling die ,19 is supported on an annular shoulder of a die holder 26 and is located by a centralizing cylindrical extension on said holder. The die holder is supported, by a threaded connection, on the upper end of an adjusting screw 27. The adjusting screw is threadably mounted in a sleeve 28 which is disposed in a receiving bore 29 in the yoke jaw 13. Sleeve 28 has a radially extending flange 30 which is seated on an annular ledge formed adjacent the upper face of the jaw. By turning the screw 27 relative to sleeve 28 the height of the dimpling die 19 relative to the jaw 13 may be regulated to accommodate sheet To facilitate such adjustment the screw 27 is provided with a knurled knob 31 secured thereon by means of a set screw 32. The degree of adjustment is visually indicated by means of a graduated ring 33 carried by the adjusting screw 27 adjacent the lower end of the sleeve 28.

Referring to Fig. 3, the die 19 has a bore 34 and counter-bore 35 providing a sliding fit for a two diameter coining ram 36. Above the bore 34 the dimpling die 19 is tapered to shape the circumference of the dimpled The coining ram 36 is supported on the upper extremity of an air loaded post which; comprises upper and lower sections 38 and 39 respectively. The main body of upper pest semen as has afsliding'fit within a centre; bore ot adjusting screw 27, While the 'redneedupper extension-or the post, on which'th'e coining ram rests, has a sliding fit in the bore of the die holder 26. The lower postl'seclien 39 is slid'ably mounted in the main bore of adjusting screw 27. The lower extremity or the post 39 rests on the upper end of an adjusting screw 4'!) which is threadabl'y mounted in the 'shoi't arm of a ram lever 41. The lever is provided with a roller bearing 42 by means of which it is mounted on a horiiontal shaft 43. Theshaft is mounted on a cylinder member 44 which has a recess 45 at its lower end to receive the lever for rocking movement therein. The frontend of the recess communicates with a vertical bore 46 in the cylinder member surrounding and fitting the adjusting screw 27 near the lower endof the latter. At the upper end of bore 46 the cylinder member abuts against the knob 31. On the lower end o t the bore '46 the cylinder member rests on a split ring 47 mounted in an annular groove in the adjusting screw 27. The split ring cooperates with the knob to restrain the cylinder member against vertical movement relative to the adjusting'screw 27. When the parts are assembled the split ring 47 is almost entirely encircled by a counter bore 49 in the cylinder member and is locked thereby in operative position in the annular groove. In order to permit the ring to be 'expanded and removed from the annular groove upon disassembly of the parts, the cylinder member is provided with an arcuate slot 50 near the lower end of the counter bore 49.

In order to adjust the position of the screw 40 relative to lever 41, the former is provided with a knob 52 fitting the lower end of the adjusting screw and locked in position thereon by means of a set screw 53. Resting atop the knob 52 is an indicator 54 which has a bore fitting over the cylindrical extension on the adjusting screw 40. Immediately above the bore is a counter bore receiving a helical spring 55 arranged to hold the indicator yieldingly in contact with the top of the knob. The indicator has an extension connected with the cylinder member to prevent rotation of the indicator. Yieldable means are provided for yieldingly locking the knob 52 and therefore the-screw 40 against turning movement relative to the indicator 54. Such yieldable means comprises a ratchet pin 56 mounted for limited reciprocation in a vertical bore in the indicator 54, and as irin 57 located in the same verticalbo're and arranged to hold the ratchet pin down in yielding locking relation to a selected one of 'a series of depressions in the upper surface of the knob 52. Suitable indicia is provided on the knob 52 and indicator 54 to show the degree of adjustment of the screw 40 relative to lever 41.

The recess 45 in the cylinder member 44 is closed at its bottom by a guard plate 58 which is detachably secured to the cylinder by a series of screws 59. The rear end of the recess 45 communicates with the lower end of a piston chamber 60. A'piston 61 is mounted for reciprocation in the chamber and is provided with an O ring 62 arranged to prevent escape of pressure fluid from the upper end of the piston chamber 60. The latter is normally closed except for a small port 63 (Figs. 1 and 9). The lower end of the piston 61 is recessed to receive the rear end of the longarm of lever 41 and to impart aforce thereto for a purpose hereinafter described. The lower end of the piston chamber 60 is closed by a cylinder cover 64 secured by the usual screws 65. The cylinder 44 is provided with a nipple 66 communicating with the piston chamber 60 by means of port 63. The nipple is connected by means of a quick coupler 67 to an airhose '68.

The hose 68 "receives live air 'ftoi'zh a pressure regulator 69. To the regulator is attached a nipple 70 whichextends upward to a pressure gauge 71. The nipple is 4 supported by a'block 72 which is attached to the side of the yoke 11.

The pressure regulator, which is shown in section in Fig. 8, is not novel per se and therefore will be described only briefly. It comprises a body 73 having attached thereto an inlet nipple 74 and an outlet nipple 75. The body has a central bore threaded at its upper and lower ends to receive a valve cage 76 and a closure plug 77 respectively. The cage provides a seat for'amovable valve member 78. The latter carries a r'earwardly projecting valve stem extending into an opening. in the cage. When the valve member is displaced below its seat, inflow of live air occurs through inlet nipple 74, inlet port 80, over the valve member and through valve cage 7'6,into chamber 81,

then through outlet port 82 and outlet nipple 75. A

compression spring 83, interposed between the valve member 78 and closure plug 77, normally retains the valve member in closed position.

The valve member 78 is arranged to be unseated by pressure responsive means. Such means includes a lower button 84 abutting thetop of the valve stem and supported at the center of a flexible diaphragm 85 which defines the top of the chamber 81. The peripheral edges of the diaphragm are clamped between the top of the body 73 and a dome 86 which is screw threaded thereon. The upper portion of the button carries a washer 87 which is urged forward by adjustable resilient means. Such means comprises a compression spring 88 seated on the washer, and an upper button 89 seated on the spring, and

an adjusting screw 90 abutting against the upper button 1 89'. The screw has a handle 91 which may be turned to regulate the pressure transmitted through the spring and buttons to'the upper end of the valve stem to unseat the valve member 78. This unseating force is opposed by the pressure of spring 83 and by the air within chamber 81. The chamber pressure corresponds with the pressure in hose line 68 which communicates at all times with the piston chamber 60 (Fig. 1).

In order to relieve the pressure quickly in piston chamber 68, when that is desired, the cylinder member 44 is provided with a drain valve 92. As shown-in Fig. 9 the valve is secured in a threaded opening in the wall of cylinder member 44 and is adapted normally to seat against an 0 ring 93 to cut off the escape of air through a cylinder port 94. By turning the valve the operator may unseat it to permit the pressure fiuid in piston chamber 60 to escape.

In operation, live air under relatively high pressure, say 90 pounds per square inch is supplied by an air hose (not shown) to the inlet nipple 74 and inlet open ing (Figs. 4 and 8) 'of the pressure regulator 69. The movable valve member 78, being held off its seat by'spring 88, permits live air to flow through the opening in valve cage 76 and then into chamber 81. As air pressure in chamber 81 builds up, it acts against the lower button 84 and diaphragm to raisethe button against the pressure of spring 88. Upon attainment of a predetermined pressure, for which the regulator is set, the valve member 78 is closed by spring 83 thus preventingfur-ther rise in pressure. The chamb'ensl is therefore maintained under a constant, relatively low pressure-of say 30 p. s. i. The chamber communicates through outlet port 82, outlet nipple 75, and hose line 68 with the piston chamber 60 in the air post cylinder member 44. The regulator chamber 81 also communicates through nipple 70 withthe gauge 71 by means of which the operator may observe the pressure in regulator chamber '81 and piston chamber 60. The air in piston cham-. ber 60 acts through piston 61, lever 41, adjusting screw 40, post sections 39, 38 and coining ram 36 to hold the ram in its uppermost position and to resist 'down-' ward movement thereof.

The work sheet '25 is first perforated with an nnder-- sized bore, that is smaller in diameter than the hole to be formed in the finished product. The sheet is initially positioned to rest upon the stationary dimpling die 19, and the dimpling punch 21 is permitted to rest upon the work sheet. The cycle of operation is then begun by the operator manually shifting the work sheet until a preformed hole is brought into registration with the punch, whereupon the punch projection 24 will drop into the hole. This movement automatically initiates the power stroke of the punch, by means of apparatus well known in the art and described for example in Fischer Patent 2,592,672 granted to applicant April 15, 1952. As the punch 21 presses down on the sheet metal 25, the reaction is transmitted back through the yoke to the rigid die 19 and the yielding ram 36. Downward driving action upon the punch 21 causes the metal to be dimpled about the opening. At the lower end of the dimple, downward movement is resisted by engagement with the flat upper face of the air loaded coining ram 36. As a result the dimple is shaped with a flat bottom immediately surrounding the projection 24. As the dimple is shaped or formed, there is a drawing action tending to stretch the upper section or layer of the material of the dimple. This stretching sets up tensile stresses which, unless counter-acted, would weaken the material and cause cracks to develop. The forging action of the air loaded coining ram 36, however counteracts or corrects this tendency to draw or thin the metal at the mouth of the dimple, and instead produces a radial outward flow of the metal as it is extruded upwardly and outwardly around the pilot portion 24.

According to the present invention, the coining or forging action of the ram 36 starts to occur with the ram in its uppermost position near the start of the dimpling operation. As a result the metal flows up wardly around the projection 24 filling the entire space between the punch 21 and die 19 thus effectively preventing overstressing and cracking of the sheet at the the mouth of the dimple. By preventing the dimpled metal from being thinned or tapered the invention assures that the dimpled metal will have the same angularity at the top and bottom, thus enabling a pair of dimpled sheets to nest perfectly.

As the punch 21 proceeds in its downward movement, the coining ram 36 yields and imparts movement through the post sections 38, 39 and adjusting screw 40 to rock the lever 41 in a counterclockwise direction, while pushing the piston 61 upward. Since the pressure of the air in piston chamber 60 is maintained constant by the regulator 69, the resistance of the coining ram 36 will be substantially uniform from the start of the dimpling operation until the completion thereof as indicated in Fig. 3. In this way the dimpling and coining operations occur simultaneously throughout the working stroke. In conventional coin dimpling apparatus employing a spring loaded ram, there is a rapid increase in coining pressure starting with a preload of, say, 1,000 pounds and ending with a much higher load of, say, 3,000 pounds. With the present invention the increase in final pressure over the preload is relatively slight, say 40%.

Another advantage of the present invention over conventional spring loaded posts is. that the air loaded post has a much greater total available force of say 6,000 pounds whereas a comparable spring loaded post would be over-stressed at a much lesser force, say, 3,000 pounds. Another advantage is that the ram 36 can be moved further, in the formation of deep dimples, without danger of breaking. Still another advantage is that the present invention provides an exact and constantly visible indication of the coining force being applied, whereas in the conventional coining apparatus the spring force can only be estimated. Still another advantage resides in the fact that adjustments can be made without the use of tools. For example, if the operator desires to increase (or reduce) the air pressure on, the

coining ram 36, he merely turns the handle 91 of the regulator 69 to increase (or reduce) the compression of spring 88. By this means the coining force can be varied in the same proportion and within a very wide range.

After the dimple has been formed, the pressure is relieved to elevate the punch 21, the work sheet 25 is removed, and the dimpled hole is drilled or reamed to a slightly larger diameter.

While the invention has been described with reference to a stationary dimplingmachine it is applicable also to portable dimplers. It may be used for either hot or cold dimpling. I

The words upper, lower, front, rear, vertical and the like are employed in the specification and claims as convenient terms for defining the position of one part of the fluid support relative to another when the assembly is held in the position illustrated'in Fig. 1, and are not intended to convey any implication that the fluid support assembly as a whole must always be mounted in the same position relative to the supporting floor or to the yoke 11.

What is claimed is:

1. Apparatus having a post arrangement including means to support the post for movement in an axial direction at substantially constant pressure, said means comprising a cylinder having a piston reciprocably arranged therein, a mechanical movement interposed between the piston and the post to multiply the reactive force of the piston against the post in an axial direction thereof, a pressure fluid connection on the cylinder, a manipulative means for adjusting the force of pressure fluid entering the cylinder by way of the pressure fluid connection, and a visible means for providing an indication of the amount of pressure in the cylinder.

2. A fluid support comprising a vertical post having an upper extremity adapted to provide a seat for a ram or the like, an adjusting screw having a bore for receiving the post with a sliding fit, a yoke for rigidly supporting the adjusting screw, threaded means interposed between the adjusting screw and yoke for raising or lowering the screw and associated post with respect to the yoke, a housing supported on said screw below the yoke, means for retaining the housing against vertical movement relative to the adjusting screw, a lever pivoted to said housing and having a plurality of pivotal arms, an abutment element carried by one arm of the lever, said abutment element providing a seat for the lower extremity of the post to resist downward movement thereof,land fluid pressure means for yieldingly resisting pivotal movement of the lever in response to downward movement of the post; and abutment element, said fluid pressure means comprising a cylinder forming part of the housing, and a piston reciprocable in said cylinder, said piston abutting against a second arm of the lever, the second arm being considerably longer than the first arm whereby to multiply the reactive force of the piston against the post.

3. A fluid support according to claim 2, in which the abutment element comprises a screw in axial alinement with the post and having a threaded connection with the short arm of the lever.

4. A fluid support comprising a vertical post, a fixed supporting element having a bore for receiving the post with a sliding fit, a cylinder housing having a vertical bore which receives the fixed supporting element near the lower end of the latter, means for retaining the housing against vertical movement relative to the fixed supporting element, the housing having a recess communicating with the lower end of the vertical bore and extending below the lower extremity of the supporting'element, the recess lying in the same vertical plane as the post, the lower end of the post projecting beyondthe lower extremity of the supporting element and into the recess, a lever mounted in said recess, a shaft supported by the housing and extending transverse to the recess and providing a pivotal support for the .lever, the recess extending. rearward from the post-and communicating at its rear end in a piston chamber provided in the cylinder housing, a piston in said piston chamber, the lever having a front arm lying below the..post and having a rear arm connected to the piston, an abutment element on the front arm providing a seat for the lower extremity of the post, fluid pressure means in said piston chamber to resist displacement of the piston in response to downward pressure exerted by the post through the lever, the rear arm of the lever being substantially longer than the front arm to multiply the reactive force of the piston against the post.

5. A fluid support according to claim 4, in which the fluid pressure means operates under substantially constant pressure during the-displacement of the piston and in which the moment armsof the lever remain substan tiallyconstant whereby the post is supported-by a substantially constant reactive force as it moves downward.

6. A fluid support according to claim 4, in which the fluid means includes pressurized air or gas and means for regulating the pressure of such air or gas to adjust the force by which the post is supported.

7. A fluid support according to claim 4, which includes means for limiting upward movement of the post relative to the fixed supporting element, said fluid means actingas a jack to raise the1post to its limit position upon removal of the force displacing it therefrom.

8. A fluid support for a vertical post comprising a fixed supporting element having a vertical bore for slidably receiving the post, a housing having nearits front end a vertical bore to receive the outside of the supporting element, a knob mounted on the supportingelement and seatedon the top of the housing to prevent the housing from moving upward relative to the supporting element, the housing having a recessin its bottom, the front end of which recess communicates with thebore in the housing, the lower'extremity'of the fixed supporting element lying within the'recess, said fixed supportingelement having an annular groove near its lower extremity, a split ring mounted in said'annular groove and engageable with the upper endof the-recess to provide a seat vfor'the housing preventing downward movement relative to the fixed supporting elenrent; a lever positioned in said recess and pivotally mounted upon' a horizontal axis transverse to the recess, said lever having an arm extending forward from-the pivot and'another arm extending rearward from the pivot, the forward arm having a vertical threaded holer substantially in alinement with the bore in the fixed supporting element,; an adjusting screw mounted in the thread-ed hol'e, the upper extremity of the adjusting screw being positioned to provide a seat for the lower extremity 8' 1 of the vertical post, the lower end of the adjusting screw projectingfbeyondv the recess and below the housing, a knob mounted. on the lower end of the adjusting screw to provide a manipulative means for turning the screw and thus adjusting the angular position of the lever with respect to the post, and fluid pressure means for engaging the-rear armof the lever to resist downward movement of the forward arm of the lever in response to pres sure transmitted through the post and adjusting screw.

9. A fluid support according to claim 8, in which the fluid means comprises a piston chamber in the housing and communicating with the rear end of the recess, a piston in the chamber and abutting against the top side of the lever near the rear end'thereof, and means for supplying pressure fluid to the piston chamber above the piston to resist upward movement of the rear arm of the lever in responseto downward pressure on the adjusting screw and front arm of the lever.

10. A fluid support according to claim 9, in which the means for supplying fluid includes a pressure regulator, said regulator having a manipulative adjusting lever, and being adapted to maintain the pressure in the piston chamber constant for any selected setting of the manipulative adjusting lever.

11. A fluid support according to claim 2 in which the cylinder provides a chamber for the piston, and which includes means for supplying the piston chamber with live air or gas undersubstantially constant pressure.

12. A fluid support according to claim 11 in which the means for supplying the piston chamber with live air or gas includes a pressure regulator.

13. A fluid support according to claim 12 in which the pressure regulator includes a manipulative element for adjusting the pressure applied to the piston chamber and hence the pressure reacting through the lever means and post to the coining ram.

14. A fluid'support according to claim 13 which includes a gauge for indicating the pressure of the air or gas in the piston chamber.

References Cited in the file of this patent UNITED STATES PATENTS

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