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Dec- 31,v 1946I
,
'
e. D. RECHTON ETAL
2,413,518
METAL FORMING MACHINE
Filed June 18, 1945
2 Sheets-Sheet l
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2,9
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680/296
Rec/7T0”
Jack H‘ Wat/0n
.
MM
ATTORNEV
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Dec- 31, 1945-
G. DfREcHToN E'ILALY
2,413,518
METAL FORMING MACHINE
' Filed June 18, 1943
2 Sheets-Sheet 2
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Geo/ye 0 Rec/van
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.mMmUNmm
A7’ TORNEY
- 2,413,518
Patented Dec. 31 ,‘ 1946
UNITED STATES PATENT OFFICE
George D. Rechton and Jack H. Watson, Los
Angeles, Calif., assignors to Douglas Aircraft
Company, Inc., Santa Monica, Calif.
Application June 18, 1943, Serial No. 491,410
14 Claims. (Cl. 153-—21)
1
pulled apart. On the other hand, a sustained‘
This invention relates to a metal forming ma
application of a lesser stress over several seconds
chine of the type in which two vertically mov
ing cooperating axially alined dies are brought
into simultaneous contact with a work article
disposed between them and particularly to a ma
chine of this character for changing the shape
or repeated separate applications of a lesser stress,
will permanently elongate the rod to the same
length without rupturing it.
rl‘he particles of
metal in the latter case “creep” slowly into their
new positions without breakage of their vcohesive
of an article, such as a dimpling machine for
bond. The same principle applies to compressive
annularly flanging a sheeted article around a
and bending stresses. Especially is this true of
perforation for receiving a rivet or other fas
repeated separate applications or a lighter stress,
tener having a conical manufactured head. The 10 if the applications are of relatively long time
invention as to some of its features is applicable
duration, such as result from percussion blows by
to any machine for forming a work article be
one die upon a work article supported by a cush
tween two reciprocatively movable dies arranged
to formingly Contact opposite sides of the work
article.
'
ioned bucking die.
It is accordingly an object of this invention
15
to provide a forming machine (and especially a
.
In dimpling and similar forming operations
upon a, work article, particularly operations in
machine for forming metal sheets such as a
dimpling machine) of improved characteristics,
volving bending, a sheet of an aluminum or mag
nesium alloy such as is used in aircraft manufac
ture, where a lightweight material is desired, ex
in which the forming operation is effected by a
v20
perience shows that if the forming is e?ected
by a single pressural contact, whether of a squeeze
succession of automatically repeated, relatively
light percussive pressures, or “shots” of the form
ing dies.
It, is another object of the invention to pro
or percussion character, of sufficient force to se
vide in such a machine means for automatically
cure the desired result, fracture weakness devel
determining the number of the relatively light
25
ops in the bend portion of the work article, and
percussive shots.
that if the same forming is eiiected by a number
It is another object of the invention to provide
of light blows, no fracture weakness results. This
in such a machine means for automatically tim
may probably be explained in part by the fact
that in the interval between two light blows the
metal molecules move into new relative positions
in which they are partially relieved of the strain
put upon them by the earlier blow, whereas if
the complete forming is eifected by one pressure
action of the dies, and particularly if that one
ing the period for effecting the succession of shots.
It is another object of the invention to provide
a stationary gun for delivering the succession of
shots, having the structural advantages of its
stationary character, and a movable lower die,
and especially a pneumatically movable lower die,
for effecting the initial pressural engagement of
action is a percussive one, because of the result 35 the dies and for initiating the automatic cycle
ing molecular movement along the initial slip
of shots of the stationary gun.
, planes which have no opportunity for equaliz
It is another object of the invention to reduce
ing, the stress is so great as to produce a move
the tendency of the sheet to warp during the
ment within these planes of such magnitude that
dimpling operation by so'constructing the ma
a stressed molecular condition within the slip 40 chine that the sheet to be dimpled is at the same
planes is created in which the ultimate stress
level at the end as at the beginning of the dim
point of the metal. is exceeded. It is also believed
pling operation and remains virtually stationary
that each light blow work-hardens the material,
during the operation.
which is another way of saying that each light
It is another object to provide pneumatic means
45
blow raises the ultimate stress point of the ma
terial, With the result that when the ?nal blow
is delivered, forming to the desired extent has
been accomplished without the metal passing the
ultimate stress point, beyond which point frac
for elevating the lower die into initial pressure
contact with the upper die of a stationary gun
and for providing a cushioned support for the
lower die when subjected to the forming shots
of the upper die.
ture soon occurs. It is a familiar fact that ii 50
It is another object of the invention to pro
a stress be suddenly applied. to
object,'as
vide a forming machine of the percussion type,
for instance a tensile stress of great magnitude
either single or multiple shot, in which the form
ing shot is delivered against an air cushioned
of metal, the rod may be permanently elongated
bucking die so as to lengthen the duration of
55
to a given length and then at that length be
for a small fractional part of a second to a rod
2,418,618
3'
c
i
p. azure period of the shot and inhibit the
pment of fracture weakness in the formed
4
with a cap 36, the piston and cap serving as a
holder for the die 28. A ?exible cup 38 secured
to the lower end of the piston 34 forms an air
seal against the inner wall of the cylinder 32
t is another object of the invention to pro—
vide a multiple shot machine of the character 5
whereby compressed air admitted through port
described having pneumatically moved dies in
49 in the Wall 42 of the arm [6 into the cylinder
which electrical means are used to manually ini
chamber 44, may elevate the piston 34. Upon
tiate the pneumatic movement of the lower die,
venting the air from the chamber 44, a coiled
to automatically initiate the actuation of the
gun upon pressural engagement of the dies, and 10 spring 46 returns the piston to its lowermostpo
to automatically terminate the actuation of the
gun.
It is another object to provide a machine to
accomplish the last mentioned purposes except
ing for an automatic instead of manual initiation
of the pneumatic movement of the lower die,
this automatic initiation being responsive to
placement of the metal sheet to be dimpled in
position upon the lower die.
sition in which a stop 49 carried by the piston
bottoms on Wall 42. This spring is seated be
tween a ring 48 secured to the lower horizontal
face of the piston 34 and the head of a bolt 59
which is mounted on the wall 42 and projects up
wardly into a recess 52 in the piston 34.
When the piston is in this position, a sheet of
metal 54 to be dimpled is placed with a previous
ly drilled perforation ?tting over a central prong
56 of the die 28. The piston 34 is then pneu
It is another object of the invention to pro- \
vide a machine of the character described hav- , 1 matically elevated, bringing the sheet 54 into con
tact with the annular nether surface 58 of the
ing pneumatically moved dies in which electrical
die 24. Air pressure then builds up in the cham
means are used to manually initiate the pneu
ber 44 to a value sufficient to initiate actuation
matic movement of the lower die in which the
pneumatic pressure thus developed is used to ini 25 of the gun 34 through a pneumatic connection
to be later described. The gun is of the well
tiate actuation of the gun and electrical means
known automatically repeating type and its pis
are used to automatically terminate actuation of
the gun.
ton is caused to deliver a succession of blows to
the upper die 24. In a manner to be hereinafter
In the drawings, which are for illustrative pur
poses only,
explained, the gun ceases operation at the end
30
of a predetermined time interval. Air pressure
Figure 1 is a perspective view of a dimpling
is then automatically lowered in the cylinder
machine embodying the invention.
chamber 44, permitting the die 28 to drop to its
Figure 2 is an elevational view, partly in sec
normal position, whereupon the sheet 54 with the
tion, of a portion ‘of the machine showing the
upper and lower dies and the mounting means of 35 completed dimple formed therein is lifted from
the lower die.
the prong 56 and removed horizontally from the
throat of the machine.
Figures 3 to 6 inclusive are diagrammatic views
The operative movements of this cycle have
showing the upper and lower dies and a metal
some novel characteristics. The gun is station
sheet to be dimpled in several relative positions
at progressive stages of the dimpling operation
40 ary. The die 24 moves downward with each blow
bending the sheet somewhat and is then retract
Figure '7 is a schematic View and wiring dia
gram of the machine.
ed by the pressure of the lower die to its initial
position preparatory to receiving the neXt blow.
Figure 8 is a schematic view and wiring dia
After each blow of the gun piston, the compressed
gram of a machine embodying the invention in
another form.
‘
7 The machine shown in Figure 1 has a frame
_ air in the chamber 44 causes the lower die to
move upward with the upper die to the extent
permitted by the partially formed dimple, the
comprising a base ill, a pedestal l2, an upper
lower die thus moving upward by increments from
arm !4 and a lower arm it, these arms de?ning
its initial metal sheet clamping position shown in
a work receiving throat 53. At the outer end
of the arm i4 is a gun housing 29 and at the 50 Figure 3 to its ?nal dimple forming position shown
in Figure 6, after which it falls back to the posi
outer end of the arm I5 is a lower die support
tion shown in Figure 2.
>
22. A female die 24, mounted for limited verti
cal reciprocative travel in the lower end of a
In the dimpllng machines as heretofore con
pneumatic percussive gun 38 mounted in the hous
structed the sheet to be dimpled initially rests on
ing 2Q cooperates with a male die 28 mounted 55 the top of the cone of the lower die and during the
on the lower die support 22 to dimple a sheet of
dimpling operation moves downwardly from this
metal placed horizontally between them and ex
initial upper level a distance equal to the entire
tending into the throat I 8.
depth of the dimple to be formed. This repeated '
The pneumatic percussion gun 30 is stationarily
mounted within the housing 20.
substantial movement of the metal sheet with
The recipro 60 successive dimpling operations results in setting
cating percussive piston of this gun strikes the
upper die 24 at the lower end of its stroke, im
parting a percussive blow thereto. The die 24
is spring held in an uppermost normal position
as shown in Figure 1. The die is shown in this 65
same normal position in the other views of the
drawings. The only movement of this die rela
up stresses in the sheet which under some condi
tions cause warping.
In a machine of this invention the metal sheet
to be dimpled, after it has been elevated into in
itial contact with the upper die, is relatively sta
tionary, its only movement being a slight up and
down movement with each blow of the gun which
tive to the machine occurs when it moves down
is but a small fractional part of the depth of the
ward a short distance against its spring support
dimple to be formed. Thus the tendency of the
in the gun 36 under a blow of the gun piston and 70 sheet to warp is decreased.
is immediately thereafter returned to its normal
The die 28 is supported on an air cushion which
position in a manner presently to be explained.
allows the die to momentarily drop under the im
The lower die support 22 is shown in Figure 2.
pact of each blow. The time of transfer of the
It comprises a cylinder 32, in which is reciproca~
energy
of the blow to the sheet metal is thereby
tively'r'nounted a piston 34, faced at its upper end 75 lengthened,
giving the slip planes of the metal
2,418,518
vate the die 28 to raise the metal sheet into con
tact with die 24. Air pressure then builds up in
the chamber 44 and conduit 68 to a value suffi
cient to close a normally open, pressure operated
electric switch I20. When this switch closes, cur
rent flows through a circuit energizing the sole
time to creep to their new‘positions with less
breakage of the molecular cohesive bond.
Figures 3 to 6 show how the flange of the dim
ple is formed with a three shot machine, illus
trating the di?erent shapes assumed by, the met
al. Fracture at the annular bend 60 (Figure 6)
is less apt to develop when the ?ange is thus
formed by a succession of bending blows delivered
hold of a normally spring-closed, solenoid-opened
air valve I36 in an air pressure line 538 leading to
the gun 30, causing the gun to apply a succession
against a cushioned bucking die instead of by one
of automatically repeated percussive blows to the
bending blow delivered against a rigidly sup 10 upper die 24. This circuit comprises conductor
ported die, for the reason stated in the introduc
I22, conductor I25, switch 620, conductor I28,
tory paragraphs hereof. In practice more. than
conductor I30 to the solenoid of air valve I36I
three shots will be found productive of better re
conductor I34 leading from the solenoid, normal
sults. The machine may be adjusted to secure
iy spring closed switch I32, and conductor I24.
any desired number of shots for each dimpling 15
The gun continues to operate until a solenoid
operation.
>
I52 opens the switch I32. The solenoid I52 is
To reduce the time of the complete cycle and
energized by an electric circuit comprising con
thereby better the efficiency of ‘the ‘machine, the
ductor I22, conductor I26, pressure switch I20,
travel of the die holder piston 34 from its inactive
conductor I28, conductor I44 to the anodes of a
20
position of Figure 2 to the position in which as
rectifier tube I42, thence to the cathodes of the
shown in Figure 3 the die 23 is held in pressural
tube I42 to an electronic timing circuit as shown.
engagement with the upper die through the work
to conductor I24. The particular arrangement of
sheet 54 should be short. The die stem 52, h0_W—
the electronic timing circuit of an electronic timer
ever, must be long in order to ?rmly hold the die
MI is no part of this invention. Suffice it to say
during the operation of the machine. According
that
current ?ows through conductor I46, sole
1y, a removable skirted cap» 35 ?ts over the die
noid I52 to the anode plate of the trigger tube
holder piston 34, and the stem 02 fits snugly both
I50 and thence to the cathode of this tube and
within a cylindrical opening 54 in the cap 36 and
conductor I24, after a lapse of time in which the
a cylindrical pocket 68 in the upper end of the
voltage inthe grid of the trigger tube I50 is built
piston 34. The length of the stem 52 being great
up over conductor I 41 and the variable resistance
er than the travel of the die 23, if the
33 and
I48. This resistance is regulated by a knob I54
piston 34 were one integral piece, it would be im
(see Fig. l) to Vary the time interval which
possible to remove the die from the die holder.
elapses between the opening and closing of air
But since the cap 38 is removable and the depth
valve I30. The heating elements of the recti?er
of the cap 36 is such that the portion of the stem 2 tube I42 are energized at all times when the
62 in the pocket 06 is shorter than the travel of
line switch 82 is closed through a circuit com
the die 28, the die may be removed by lifting the
prising conductor I22, conductor I40 and con
cap and die until the stem 62 clears the upper
ductor I24. The ‘solenoid I55 of a normally closed
horizontal face of the piston 34 by then moving
"clean-up switch I5'I holds the switch I5'I open
40
the assembled cap and die laterally clear of the
when the pressure switch I20 is closed, allowing
piston, after which the die may be removed from
the timer to function. When switch I20 opens
the cap and replaced by another die, which may
in response to a reversal of valves ‘I2 and ‘I3
be installed in the holder by reversing the steps
e?ected by opening foot switch I04, then switch
of removal.
I5'I closes and the voltage of the grid of trigger
Figure '7 shows schematically the control sys— 45 tube I50 drops to zero. The machine is now re
tern by which the machine is operated. The pis
conditioned for the next dimpling operation.
ton 34 is elevated by compressed air conducted
An alternative embodiment of the machine is
thereto in a conduit til which is supplied from a
schematically shown in Figure 8. In this em
suitable source through a conduit ":2 having a 50 bodiment, the gun and cylinder chamber 44 are
normally closed, solenoid opened valve ‘I2; The
subject to the same degree of air pressure. When
conduit 68 is vented to lower the piston 34
the lower die is raised into pressural contact with
through an exhaust conduit ‘I4 controlled by a
the upper die through the work article and the
normally open, solenoid closed valve ‘I8.
air pressure thereafter rises to a predetermined
The solenoid of valve ‘E0 is energized by‘ an elec
value, the gun is actuated to deliver a succession
tric circuit comprising conductors 84 and 85,
of blows. The air pressure is brought to bear on
switch 88 (which is normally spring biased to con
both cylinder chamber and gun by closing ‘the
tact the terminal of conductor 92), conductor as
to the solenoid, conductor 32 from the solenoid
foot switch and is cut off by the electronic timer.
In this view the designating numbers are the
and conductor 94. Conductors 84 and 94 are con
same as those of Figure ‘7 on those parts which
nected to power leads ‘I8 by a line switch 82. The 60 are common to the two machines, additional
solenoid of valve ‘I2 is energized by an electric
numbers being used to designate parts of the
circuit comprising conductor ‘84, conductor 85,
modi?ed machine which are not present in the
machine of Figure 7.
to contact the terminal of conductor 06, con~
A branch air line I58 is T’d into air line I38.
ductor 86 to the solenoid of valve ‘I2, conductor 98
Line I58 leads to the cylinder chamber 44. The
from this solenoid, and conductor 94.
solenoid of air valve I36 is closed by a circuit
The solenoid 80 is energized by a circuit com
comprising conductor 84, conductor 85. switch
prising conductor 84, conductor I58, normally
88 (when moved to the right by solenoid 80 in
open foot switch I 84 when the latter is held down
contact with the terminal of conductor I58),
in closed position by the foot of the operator, con 70
conductor I14 to the solenoid of air valve I36,
ductor H0 to the solenoid 80, conductor IE2 from
conductor I34 from this solenoid, switch I32, con
switch 88 when moved by solenoid 80 to the right
solenoid 88 and conductor 94.
'
When the foot switch 194 is closed, ener'gizing_;_-_v
solenoid 84, valve ‘it closes ‘and valve ‘#2 opens,v
admitting compressed air into chamber 44 to ele-v
ductor I30 and cond 1‘
v 84.
Solenoid 80 pulls
switch 88 to the right rpm dead contact I66 to
the terminal of Contact I58 when energized by
2,413,518
7
an electric circuit comprising conductor 94, con
ductor IIZ tosolenoid 80, conductor I52 from
solenoid 89, foot switch I 04, conductor I64 and
8
and a spring arranged to lower said piston upon
the venting of said cylinder.
.
4. In a metal forming machine, the combina
tion of: ?rst and second, axially aligned, axially
Solenoid I52 is energized to break the circuit
operating the solenoid of air valve I36 by an elec 5 relatively movable die holders; means limiting re
tractive axial movement of the die holders rela
tric circuit comprising conductor I44 leading
tive to each other in excess of a predetermined
from conductor I58 to recti?er tube I42 and the
spacing; ?rst and second dies forv said ?rst and
other elements of the electronic timer MI and
conductors its and 94 leading from the timer. 10 second die holders respectively, said second vdie
having a mounting shank and said second die
The heating elements of the recti?er tube are
holder
being recessed to receive said shank; and a
energized by connections to conductors I ‘I0 and
facing block on the die receiving end of said sec
I12 as shown.
,,
_
1
ond:die holder, said block being held in axial
In the operation of the machine, shown in
alignment
with said second die holder and having
Figure 7, the line switch 82 is closed, and the 15
a through opening to receive said shank, said
sheet 54 to be dimpled placed in position on the
shank being longer than said predetermined
lower die. Valve ‘I2 is opened and valve 16 closed
spacing
and the linear di?erence between the
by closing the foot switch IM, causing the lower
length of said shank and the thickness of said
die 28 to be elevated until the sheet 56 is pres
block being shorter than said predetermined
surally held between the dies. Pressure is built up 20 spacing.
,
.
to operate valve I20 to apply air pressure to the
5.
In
a
forming
machine,
the
combination
of
:
gun 33 which then delivers percussive blows to
upper and lower cooperating forming dies, said
the upper die until cut off by the electronic timer.
dies being mounted for relative movement on said
The foot switch I04 is then opened.
machine;
means for bringing the dies into simul
The time interval of the cycle of each single 25 taneous pressural
contact with a work article to
shot is constant at any given line pressure. Con~
be formedymeans responsive to a predetermined
sequently, regulation of the resistance I48 de
pressural contact for applying a succession of
termines both the duration of the time period of
automatically repeated relatively light percussion
actuation of the gun and the number of shots.
blows to the upper die during said pressural con
The line pressure is indicated on the pressure 30
tact; means for bucking the lower die during said
gauge I 56 (Figure 1).
application; and means made operative simulta
In the machine of Figure 8, closing the foot
neously
with said pressure-responsive means for
switch Hit operates the air valve I36 to ?rst ele
automatically terminating said succession of
conductor 84.
.
.
vate the lower die and then actuate the gun, the
gun ceasing operation when the air valve I33 is
closed by the electronic timer.
blows at the completion of a predetermined num—
ber thereof.
-
'
What is claimed is:
1. In a metal forming ‘machine, the combina
6. In a forming machine, the combination of:
upper and lower cooperating forming dies, said
tion of : an upper automatic-cycle pneumatically
said machine; means for bringing the dies into
dies being mounted for relative movement on
operated hammer gun having a stationary cyl 4-0 simultaneous pressural contact with a work ar
inder and a piston hammer slidably engageable
ticle tobe formed; means responsive to a prede
therewith and arranged to deliver percussive
termined pressural contact for applying a succes
blows; a limitedly vertically reciprocatable ?rst
sion of automatically repeated relatively light
die arranged to receive the blows of said hammer
percussion blows to the upper die during said
and to have contact engagement with a work 45 pressural contact; means for bucking the lower
piece when in its uppermost position; a station
die during said application; and time controlled
ary lower die support; a die holder reciprocatively
means made operative simultaneously with said
movable on said support; a second die on said
pressure-responsive means for terminating said
die holder; means for elevating said die holder
succession of blows after a predetermined elapsed
relative to said support to a position such as to 50 period of time.
‘
_
press a work piece between said dies; means re
7. The combination de?ned in claim 5 in Which
sponsive. upon said elevation, to the pressure be
tween the dies for initiating the automatic cycle of
the hammer gun to cause the gun hammer to
strike the ?rst die.
2. In a metal forming machine, the combina
said means for applying contact consists of means
for applying ?uid pressure of progressively in
creasing value as a bucking support to said sec
55 end die and the operation of said means for ap
tion of : an upper automatic-cycle pneumatically
operated hammer gun having a stationary cyl
inder and a piston hammer slidably engageable
therewith and arranged to deliver percussive 60
blows; a limitedly vertically reciprocatable ?rst
die arranged to receive the blows of said hammer
and to have contact engagement with a work
piece when in its uppermost position; a lower sta
plying a succession of automatically repeated
blows is automatically initiated by said ?uid pres
sure upon said ?uid pressure reaching a prede
termined value.
-
1
8. Ina forming machine, the combination of :
upper and lower cooperating forming dies; a sta
tionary pneumatic gun for the upper die con
structed to deliver a- succession of automatically
repeated relatively light percussion blows to the
tionary pneumatic cylinder; a piston for said 65 upper die; a pneumatic cylinder-piston means
cylinder; a second die on said piston; means for
movably supporting the lower die; means for
admitting compressed air to said cylinder to ele
supplying air under pressure to said cylinder-pis
vats said piston to a position. such as to press a
ton means; venting means for said cylinder-pis
work piece between said dies; and means respon
ton means; means for alternatively connecting
sive to a predetermined air pressure in said cyl
inder for initiating theautomatic cycle of the 70 said air supplying and venting means to the cyl
inder-piston means; a valved conduit for supply‘
gun, causing the gun ‘hammer to strike the ?rst
ing air under pressure to the gun; an electric cir
cuit for opening'said valve, energized-in response
3. The combination de?ned in claim 2 and in
to a predetermined pressure in said cylinder pis
addition thereto; means for venting said cylinder; 75 ton means; and a simultaneously energized elec
die.
.
-
-
-
2,413,518
der and a piston hammer slidably engageable
tronic timer for de-energizing said circuit to close
said valve.
9. The combination de?ned in claim 8 in which
therewith and arranged to deliver percussive
blows; a limited vertically reciprocatable ?rst
dimpling die arranged to receive the blows of said
hammer and resiliently held to a lowermost posi
tion and to have contact engagement with a work
piece when in any position of said ?rst dimpling
said means for alternatively connecting said air
supplying and venting means to the cylinder pis
ton means comprises an electrically opened, nor
mally closed inlet valve; an electrically opened,
die; a stationary lower die support; a die holder
reciprocatively movable on said support; a second
normally closed exhaust valve; a switch, spring
biased to close an electric circuit to open the ex
dimpling die cooperatively shaped and related to
haust valve and electromagnetically operated to
said ?rst dimpling die and mounted on said die
holder; means for elevating said die holder rela
tive to said support to a position such as to press
a work piece between said dies; and means re
close an electric circuit to open the inlet valve;
and a manually closed circuit to energize said
electromagnet.
10. In a forming machine, the combination of:
upper and lower cooperating forming dies; a sta- '
tionary pneumatic gun for the upper die con
structed to deliver a succession of automatically
repeated relatively light percussion blows to the
upper die; a pneumatic cylinder-piston means
movably supporting the lower die; a common con
duit system co-mmunicatively connecting said gun
and cylinder piston means to each other; a nor
mally closed valved conduit connecting said con
duit system with a source of air pressure; a
solenoid for opening the valve of said valved con
duit; a manually operated switch for energiz
ing the circuit of said solenoid; an electronic timer
sponsive, upon said elevation, to the pressure be
tween the dies for initiating the automatic cycle
of the hammer gun to cause the gun hammer to
strike the ?rst dimpling die.
13. In a dimpling machine the combination of 2
an
upper dimpling die; a lower dimpling die;
20
means limiting the upward movement of the up
per dimpling die; means for pressurally urging
the lower die against the work sheet and the work
» sheet against the upper die and the upper die
against said limiting means; and means for apply
25 ing a succession of relatively light percussive
blows to the upper die against the action of said
pressural urging means of such a force relative to
said pressural action that only a fractional por
erated switch; a normally closed switch in said
tion of the dimple is formed with each blow,
solenoid energizing circuit; and a solenoid con 30 the upper die and work sheet at each blow mov
trolled by said timer for opening said last men
ing ?rst downwardly a fraction only of the depth
tioned switch, said gun being actuated by a higher
of the dimple cone of the upper die and then up
pneumatic pressure than that required to‘ cause
wardly to said limiting means under the pressural
said cylinder piston to move said lower die.
action of the urging means againstthe lower
11. In a metal forming machine, the combina 35 die, said urging means moving said lower die up
tion of: an upper automatic-cycle pneumatically
wardly to a new position after each blow applied
operated hammer gun having a stationary cylin
to said upper die to hold the work piece against
der and a piston hammer slidably engageable
the upper die during the dimpling operation.
therewith and arranged to deliver percussive
14. In a dimpling machine, the combination of:
blows; a limited vertically reciprocatable ?rst 40 ?rst and second cooperating dies; means includ
die arranged to receive the blows of said hammer
ing means for applying ?uid pressure of progres
and resiliently held to a lowermost position and
sively increasing value against said second die
to have contact engagement with a work piece
to move the same toward said ?rst die and bring
When in any position of said ?rst die; a stationary
the dies into simultaneous pressural contact
lower die support; a die holder reciprocatively 45 ing
with a sheet of metal to be dimp-led; and means
movable on said support; a second die on said die
made operative by said ?uid pressure upon said
holder; means for elevating said die holder rela
?uid pressure reaching a predetermined value for
tive to said support to a position such as to press
applying a succession of automatically repeated
simultaneously energized by said manually op
a work piece between said dies; and means re
light percussion blows to said ?rst die
sponsive, upon said elevation, to the pressure be 50 relatively
during
said
pressural contact, the ?uid pressure
tween the dies for initiating the automatic cycle
applying means bucking the second die during
of the hammer gun to cause the gun hammer to
the application of said blows.
strike the ?rst die.
12. In a metal forming machine, the combina
GEO. D. RECI-ITON.
tion of: an upper automatic-cycle pneumatically
JACK H. WATSON.
operated hammer gun having‘ a stationary cylin
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