U.S. patent number 3,726,000 [Application Number 05/146,639] was granted by the patent office on 1973-04-10 for means for fastening overlying metal sheets.
Invention is credited to Otto Paul Hafner.
United States Patent |
3,726,000 |
Hafner |
April 10, 1973 |
MEANS FOR FASTENING OVERLYING METAL SHEETS
Abstract
A longitudinally extending pierce and forming punch having a
free end face is mounted on the base of a double-acting press that
has first and second independently actuatable rams. Rigidly mounted
on the first ram is a pierce and forming die having a punch
receiving aperture into which the pierce and forming punch is
receivable when the first ram is actuated. De-actuation of the
first ram clears the die from the pierce and forming punch exposing
its free end face. A flattening punch rigidly mounted on the second
ram is slideably mounted in the punch receiving aperture in the die
and is cooperable with the end face of the pierce and forming punch
when the second ram is actuated.
Inventors: |
Hafner; Otto Paul (Cherry Hill,
NJ) |
Family
ID: |
22518288 |
Appl.
No.: |
05/146,639 |
Filed: |
May 25, 1971 |
Current U.S.
Class: |
29/21.1; 29/432;
29/521; 403/283; 29/509; 403/282; 403/285 |
Current CPC
Class: |
B21D
39/00 (20130101); Y10T 403/4974 (20150115); Y10T
29/49915 (20150115); Y10T 29/34 (20150115); Y10T
403/4991 (20150115); Y10T 403/4966 (20150115); Y10T
29/49833 (20150115); Y10T 29/49936 (20150115) |
Current International
Class: |
B21D
39/00 (20060101); B23p 017/00 () |
Field of
Search: |
;29/21.1,509,432,521
;113/116FF ;287/189.36D |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Moon; Charlie T.
Claims
The following is claimed:
1. Punch and die set means to fasten overlying planar metal sheets
using a double acting press having separately actuatable
longitudinally movable first and second rams mounted on a rigid
base, comprising:
a. a longitudinally extending pierce and forming punch rigidly
mounted on said base and having a free end face with diametrically
opposed relieved portions therein;
b. a cutting and forming die rigidly mounted on said first ram for
movement therewith and having a longitudinally extending punch
receiving aperture into which said piercing and forming punch is
receivable when said first ram is actuated;
c. a flattening punch rigidly mounted on said second ram for
movement therewith and longitudinally slideably received in said
punch receiving aperture; and
d. said flattening punch being cooperable with the end face of said
pierce and forming punch when said second ram is actuated.
2. Punch and die set means according to claim 1 including means to
sequentially operate said first ram and then said second ram.
3. Punch and die set means according to claim 1 including a
stripper table adapted to support said sheets and resiliently
mounted on said base for limited longitudinal movement, and having
a clearance aperture for said pierce and forming punch.
4. Punch and die set means according to claim 3 wherein said pierce
and forming punch as a periphery comprising a piercing edge and a
bending edge whereby actuation of said first ram causes said die to
clamp said sheets to said table and said pierce and forming punch
to pass through the aperture in said table and displace a section
of said sheets out of the plane thereof and into said punch
receiving aperture by piercing a portion of the periphery of said
section and bending the remainder thereof.
5. Punch and die set means according to claim 4 wherein
de-actuation of said first ram causes said die to be retracted
until the displaced section of said sheets is clear of said punch
receiving aperture.
6. Punch and die set means according to claim 5 wherein actuation
of said second ram causes the displaced section of said sheets to
be swaged between said flattening punch and the free end face of
said pierce and forming punch whereby the pierced portion of said
section is laterally moved and caused to overlie the edge of said
sheets from which said pierced portion was severed.
7. Punch and die set means according to claim 6 wherein the free
end of said pierce and forming punch is curved, and the free end of
said flattening punch is curved to a lesser extent than the
curvature of the free end face of said forming punch.
8. Punch and die set means according to claim 6 wherein
de-actuation of said second ram releases the swaged section to
effect removal of said sheets.
Description
DETAILED DESCRIPTION
This invention relates to a method and means for fastening
overlying metal sheets utilizing a punch and die set mounted in a
double-acting press having two separately actuatable rams.
It is conventional to fasten overlying sheets by partially piercing
and deforming sections of the sheets. Such a process eliminates the
need for a separate fastener and is adequate for sheet metal joints
used in forming ducts or the like. So simple is this integral
connection to fabricate that many such connections can be made to
provide a joint of adequate strength against both tension and
torsion.
In making this integral connection, overlying sections of
superposed metal sheets are displaced out of the plane of the
sheets by piercing a portion of the periphery of the sections and
bending or forming the remainder thereof. The displacement is such
that the lower surface of the displaced section is even with the
upper surface of the top of the two sheets. By swaging and or
flattening the displaced section, the resultant lateral growth of
the section causes its pierced edges to overlie the edges from
which the section was pierced.
Conventionally, this type of connection is achieved using a process
that requires two stations, one to pierce and displace the section,
and one to swage the displaced section. Apparatus is known,
however, in which all of the steps take place at one station. This
latter apparatus includes a punch and die set wherein, in a single
stroke, initial movement achieves the piercing and displacing of
the section, and final movement achieves the swaging. To
accommodate the resultant lateral growth of the section, the die
must be provided with an expandable portion that is initially set
to provide sufficient clearance for the piercing operation. As the
swaging begins, the growth of the section forces the movable
portion of the die to expand against a spring load. An example of
this design is shown in U. S. Pat. No. 2,811,880, issued Nov. 5,
1957.
While the conventional apparatus may be adequate for many purposes,
the expandable feature of the die is a possible source for
maintenance problems when volume production is required.
Accordingly, it is the primary object of the present invention to
achieve a fastener of the type described at one station without the
necessity for having a die requiring a movable section operated by
the lateral growth of the section of the fastener as such section
is swaged or flattened.
Briefly, this and other objects of the invention are achieved by
employing a double acting press having two separately actuatable
rams. Rigidly attached to the base of the press is a pierce and
forming punch having a free end face. A cutting and forming die is
rigidly mounted on one of the rams and has a punch receiving
aperture therein into which the pierce and forming punch is
receivable when the one ram is actuated.
The periphery of the pierce and forming punch surrounding its free
end face has a first portion that closely matches a corresponding
portion of the punch receiving aperture of the die to provide a
fixed die clearance that achieves a piercing of a portion of the
periphery of the section that is displaced from the plane of the
sheets by actuation of the first ram. A second portion of the
periphery of the pierce and forming punch is relieved and widely
spaced from a corresponding relieved portion of the punch receiving
aperture of the die. Such second portion causes bending and
stretching of the portion of the periphery of the displaced section
that is not pierced. The design is such that the section is
displaced beyond the plane of the sheets and held there by the
pierce and forming punch. The stresses in the bent and stretched
portion of the displaced section resiliently urge the displaced
section toward the sheets.
Rigidly mounted on the other ram is a flattening punch that is
slideably received in the punch receiving aperture in the die.
After the first ram is actuated to achieve the desired piercing and
displacing of a section of the overlying sheets, it is then
deactuated or moved clearing the die from the punch receiving
aperture and freeing the displaced section for lateral expansion.
Such expansion occurs when the second ram is actuated swaging and
flattening the section between the flattening punch and the end
face of the pierce and forming punch. In addition, the release of
the displaced section by the pierce and forming punch permits the
residual stresses in the bent and stretched portion of the
displaced section to resiliently urge the laterally expanded
section toward the sheets forming a secure connection therewith.
This arrangement thus produces the desired integral fastener at one
station by a two-step process that eliminates the special type of
die required by the prior art.
The features of this invention for which protection is sought are
pointed out with particularity in the appended claims. The
invention itself, however, both as to its organization and method
of organization, together with further objects and advantages
thereof, may best be understood by reference to the following
description taken in connection with the accompanying drawings,
wherein like parts in each of the several figures are identified by
the same reference character, and wherein:
FIG. 1 is a top view of a fragment of a pair of superposed metal
plates showing an integral connection made in accordance with the
present invention;
FIG. 2 is a section taken along the lines 2--2 of FIG. 1;
FIG. 3 is a section taken along the lines 3--3 of FIG. 1;
FIG. 4 is a sectional view of a double acting press into which the
novel punch and die set of the present invention has been
incorporated, the parts of such set being shown just prior to the
piercing and displacing step in forming the integral connection
shown in FIG. 1;
FIG. 5 is a sectional view like FIG. 4 but shows the parts after
the first ram has been actuated and the piercing and displacing
step has been completed;
FIG. 6 is a sectional view like FIG. 4 but showing the parts after
the first ram has been de-actuated and the die about to be cleared
from the pierce and forming punch;
FIG. 7 is a sectional view like FIG. 4 but showing the parts after
the second ram has been actuated;
FIG. 8 is a perspective view of the free end face of the pierce and
forming punch; and
FIG. 9 is a perspective view of the cutting and forming die showing
details of the punch receiving aperture.
Referring now to FIGS. 1 - 3, integral connection 10 is shown in
superposed metal sheets 11 and 12. Connection 10 comprises a pair
of overlying sections 13 displaced out of the planes of each of the
sheets. This configuration is achieved by piercing opposite
portions 14 and 15 of the periphery defining the sections and
bending the remainder of the two opposite portions 17 and 18 of the
periphery. The displacement of sections 13 is such that the lower
surface 19 of sections 13 must be held above the upper surface 20
of the top sheet 11 against the stresses developed by stretching
portions 17 and 18 by which the sections remain attached to sheets
11 and 12.
After this displacement has taken place, sections 13 are flattened
and swaged to effect lateral growth of the sections in a direction
aligned with pierced portions 14 and 15. Such lateral growth is
sufficient to cause the pierced edges 21 to overlie the edges 22
from which sections 13 were pierced. Upon the release of sections
13, the residual stresses in portions 17 and 18 urge the laterally
expanded pierced edges 21 into resilient engagement with the top
surface of sheet 11 adjacent edges 22. As a consequence of this
construction, an integral fastener is achieved because edges 21 in
cooperation with edges 22 prevent separation of sheets 11 and
12.
To develop the connection shown in FIGS. 1 - 3, a double acting
press 30 (shown schematically in FIGS. 4 - 7) is used in connection
with the punch and die set 31 of the present invention. Press 30
includes a rigid base 32, first and second rams 34 and 33,
independently actuatable by control means 35 for longitudinal
movement relative to the base, and stripper table 36 resiliently
mounted on base 32. Punch and die set 31 comprises three elements:
pierce and forming punch 37, cutting and forming die 38 and
flattening punch 39.
Considering stripper table 36 first, it comprises a planar support
40 adapted to provide a horizontal support for the metal sheets to
be fastened, and a plurality of vertical round posts 41 rigidly
fastened to the support on the underside thereof adjacent the
periphery of the support. Posts 41 are mounted in anti-friction
bearings 42 attached by blocks 43 to base 32. The bearings limit
movement of support 40 to the vertical or longitudinal direction.
Centrally located in support 40 is clearance aperture 44 into which
forming punch 37 projects.
Punch 37 extends longitudinally upwardly from base 32 and is
rigidly mounted thereon by means of holder 45 which includes block
46 attached to base 32, punch holder 47 and adjusting screw 48.
Punch holder 47 is provided with a longitudinal aperture receiving
one end 49 of punch 37 which is provided with a transverse recess
for receiving set screw 50 that locks and orients the punch. Screw
48 can be adjusted to provide the necessary vertical positioning of
end face 51 of punch 37 which is on end 52 of the punch opposite
end 49. As shown in FIG. 4, coiled spring 53 surrounds punch 37 and
has one end abutting holder 45 and the other end abutting the under
side of support 40. By this arrangement, the top of support 40 is
resiliently held above end face 51 of punch 37 which is received in
aperture 44, permitting overlying sheets 11 and 12 to be placed on
support 40 without being interfered with by punch 47.
Turning now to forming die 38, it is rigidly mounted on first ram
34 for movement therewith. Specifically, die 38 is cylindrical in
shape having flange 54 at one end receivable into a counterbored
recess in the lower face of ram 34 and held there by block 55 which
may be bolted to the lower face of the ram.
Forming die 38 has a longitudinally extending punch receiving
aperture 56 for receiving displaced section 13 and the top of punch
37 when the first ram is actuated. Punch 37 is essentially
cylindrical, and its end face 51 is essentially dome shaped with a
central flat region 57 (FIG. 8) and a pair of opposite relieved
portions 58 defined by a pair of opposite longitudinal recesses 59
formed in the periphery of end 52 of the punch. Aperture 56 in die
38 closely matches the configuration of end face 51 of punch 37.
Thus, aperture 56 is essentially cylindrical, but has a pair of
opposite relieved portions 60 formed by longitudinal recesses 61.
By means of suitable keys, relieved portions 58 on punch 37 are
aligned with relieved portions 60 in aperture 56 of die 38.
When ram 34 is actuated by control means 35, die 38 descends, and
end face 61 thereof engages top sheet 11 as shown in FIG. 4.
Thereafter, continued longitudinal movement of ram 34 imparts
longitudinal movement to sheets 11, 12 and support 40 against the
resistance of the sheets to piercing and bending, and against the
resilient force of spring 53. At the end of the stroke of ram 34,
displaced section 13 is removably received in aperture 56 of die
38. During the final movement of ram 34, the cylindrical portions
of punch 37 between relieved portions 58 cooperate with the
cylindrical portions of die 38 between relieved portions 60 and
achieve the desired bending and stretching of the sheets as
indicated by numerals 17 and 18 in FIG. 1. At this stage, the
bottom edges of displaced section 13 are shown in the drawing as
being aligned with the top surface of sheet 11. Actually, the
bottom edges of displaced section 13 are slightly above the top
surface being held against the residual stresses in portions 17 and
18 by punch 37.
After ram 34 completes its stroke, ram 33 is actuated by control
means 35 and ram 34 is de-actuated. Rigidly attached to ram 33 is
flattening punch 39 which is slideably received in aperture 56 for
movement relative to die 38. Punch 39 is provided with a
longitudinal peripheral slot 62 into which key 63 projects to
maintain the alignment of die 38.
The timing of the actuation of ram 33 and the de-actuation of ram
34 by control means 35 is such that end face 61 of die 38 begins to
clear top sheet 11 as the concave surface 64 of punch 39 begins to
engage section 13 as shown in FIG. 6. This arrangement permits
support 40 to remain depressed and for section 13 to remain engaged
with end face 51 of punch 37.
By the time ram 33 reaches the end of its stroke, as shown in FIG.
7, section 13 atop face 51 is cleared from aperture 56 in die 38.
Section 30 is then swaged between concave surface 64 of punch 39
and end face 51 of punch 37 as ram 33 reaches the end of its
stroke. The curvature of dome 51 is somewhat less than the
curvature of surface 64 and the flattening and swaging of section
30 results in its lateral growth as shown in FIGS. 2 and 3 until
the pierced edges of the section overlie the edges of the sheets
from which the section was pierced.
The timing of the actuation of ram 33 and the de-actuation of ram
34 is important because it is essential that the stripper table not
release the sheets from punch 37 until the swaging operation is
completed and ram 33 is de-actuated. Control means 35 in a
conventional manner exerts the necessary dynamic control on rams 33
and 34.
After the swaging operation is complete, ram 33 is deactuated and
the rams then return to a position at which the resilient mounting
of stripper table is effective to remove punch 37 from section 30.
In this condition, punch 37 releases section 13 as previously
described, and the sheets can be indexed to place another portion
over punch 37, in preparation for making another integral
fastener.
* * * * *