U.S. patent number 3,625,262 [Application Number 04/828,822] was granted by the patent office on 1971-12-07 for conductor wrapping bit and method for forming a surface thereon.
This patent grant is currently assigned to Gardner-Denver Company. Invention is credited to William J. Baker, Richard J. Hurst.
United States Patent |
3,625,262 |
Baker , et al. |
December 7, 1971 |
CONDUCTOR WRAPPING BIT AND METHOD FOR FORMING A SURFACE THEREON
Abstract
A rotary bit for wrapping conductor wire about a terminal in
helical convolutions to form an electrical connection. The bit
includes a longitudinal terminal-receiving bore and a conductor
wire-receiving groove in radially offset parallelism therewith. A
wire-camming surface slopes radially inwardly from the transverse
end face of the bit to the terminal bore and includes a helical
rise for continuously camming and supporting a major portion of
successive wire convolutions. A wire guide surface intersects the
conductor groove and sloped camming surface for feeding the wire
into camming position. The sloped camming surface is formed by a
rotary form machining tool which is simultaneously rotated relative
to the bit longitudinal axis and axially moved relative to the bit
end face.
Inventors: |
Baker; William J. (Reed City,
MI), Hurst; Richard J. (Hersey, MI) |
Assignee: |
Gardner-Denver Company (Quincy,
IL)
|
Family
ID: |
25252830 |
Appl.
No.: |
04/828,822 |
Filed: |
May 29, 1969 |
Current U.S.
Class: |
140/124; 29/753;
242/439.3 |
Current CPC
Class: |
H01R
43/033 (20130101); Y10T 29/53235 (20150115) |
Current International
Class: |
H01R
43/033 (20060101); B21f 003/02 (); B21f
015/00 () |
Field of
Search: |
;29/23H,23DT
;140/117,118,119,122,124 ;242/7.17,7.06 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Combs; E. M.
Claims
What is claimed is:
1. A bit for wrapping a wire about a terminal in helical
convolutions comprising:
a. a bit end face;
b. a terminal-receiving bore in said end face;
c. a wire-receiving groove opening to said end face;
d. a helically sloped wire camming surface disposed about said
terminal-receiving bore; and,
e. surface means intersecting said wire-receiving groove and said
wire-camming surface and sloping axially with respect to the
longitudinal axis of said bit from said intersection with said
wire-camming surface to said intersection with said wire receiving
groove, said surface means including a substantially funnel-shaped
section converging from said intersection with said wire-receiving
groove to said intersection with said wire-comming surface; for
guiding said wire into a position for camming said wire onto said
terminal by said wire-camming surface.
2. The invention set forth in claim 1 wherein:
the longitudinal axis of said funnel-shaped section lies in a plane
parallel to the longitudinal axis of said bit.
3. In a bit for wrapping a wire about a terminal in helical
convolutions:
a. a bit end face;
b. a terminal-receiving bore in said end face;
c. a wire-receiving groove opening to said end face; and,
d. a wire camming and support surface disposed about said
terminal-receiving bore and sloping radially inwardly with respect
to the longitudinal axis of said bit, said camming and support
surface having a helical lead corresponding substantially to the
lead of a wire convolution for compressively embracing a major
portion of the periphery of a wire convolution and pressing said
wire convolution radially against said terminal.
4. A bit for wrapping a wire about a terminal in helical
convolutions comprising:
a. a bit end face;
b. a terminal-receiving bore in said end face;
c. a wire-receiving groove opening to said end face;
d. surface means on said bit for camming said wire onto said
terminal; and,
e. wire guide surface means intersecting said wire-receiving groove
and sloping axially toward said bit end face for guiding said wire
into a position for camming said wire onto said terminal by said
wire-camming surface means, said wire guide surface means
comprising a substantially funnel-shaped portion converging from
said intersection with said wire-receiving groove toward said bit
end face.
Description
BACKGROUND OF THE INVENTION
Conductor-wrapping tools commonly incorporate a bit which is
connected with a rotary motor and journaled in a surrounding
stationary sleeve. The bit is usually provided with a longitudinal
bore for receiving an electrical terminal and a radially offset
groove for receiving a stripped end portion of a wire which is to
be wound in helical convolutions about the terminal upon rotation
of the bit.
Known conductor-wrapping bits include types having surfaces opening
to the end face of the bit which operate to cam portions of the
conductor wire radially inwardly onto the terminal as the winding
process is carried out. This camming action enhances the electrical
and mechanical integrity of the connection in various ways.
Conductor-wrapping bits known in the art which have sloped camming
surfaces are disclosed in U.S. Pat. No. 2,758,797 to E. P. Miklau
and U.S. Pat. No. 3,078,052 to W. L. Olds et al. The
conductor-wrapping bit of Miklau provides a helical sloped surface
for camming the end portion of the wire, and the wrapping bit of
Olds provides a sloped surface for radial and axial camming of
portions of each wire convolution as well as the end portion.
A longstanding problem in the art of conductor-wrapping bits has
been the provision of a bit which will compensate for dimensional
variations of the terminal and wire to provide the proper amount of
camming action to assure consistency of the mechanical and
electrical characteristics of connections. The criticality of
providing the structural essentials for a satisfactory wrapped
electrical connection is discussed in detail in U.S. Pat. No.
2,759,166 to R. F. Mallina.
Another problem in the art of wrapping bit design is the provision
of adequate contact area between the bit surface and the conductor
so that wear producing unit pressures between the bit surface and
the conductor may be held within reasonable limits. This problem
has been substantially solved with the improved wrapping bit
disclosed in U.S. Pat. No. 3,531,056 issued to applicants on Sept.
29, 1970. Ser. No. 683,631 filed by applicants on Nov. 16, 1967.
However, the wrapping bit disclosed in Ser. No. 683,631 does not
compensate for dimensional variations encountered in mass produced
terminals and conductor wire.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a
conductor-wrapping bit which operates to wrap a conductor wire in
successive helical convolutions about a terminal with consistency
of mechanical and electrical characteristics regardless of
dimensional variations which are normally encountered in mass
produced terminals and wire. The present invention further provides
a wrapping bit having a wire camming and support surface which
operates to cam a major portion of a wire convolution radially
inwardly with respect to the bit axis of rotation and axially
forwardly away from the bit end face to assure a properly wrapped
connection. By engaging and supporting a major portion of a wire
convolution, unit pressure between the bit and wire is reduced;
and, accordingly, lateral deflection of the terminal is
reduced.
The functional advantages of the present invention are realized in
the wrapping operation by a wrapping bit having a camming surface
which substantially surrounds the terminal receiving bore and
slopes radially inwardly from the transverse end face of the bit to
the terminal-receiving bore whereby the wire is cammed onto the
terminal over a major portion of each convolution regardless of
dimensional variations in terminal and wire cross section.
Furthermore, the bit camming surface is provided with a helical
rise conforming substantially to the natural helix of a wire
convolution to provide for reduced contact stress between the bit
surface and the wire and to provide uniform camming action. The
present invention further includes a wire guide surface
intersecting the conductor receiving groove and the sloped camming
surface which is operable to feed the wire into the most desirable
camming position between the terminal edge and the bit camming
surface.
The present invention also provides a novel method for forming a
helical sloped surface on a conductor-wrapping bit by
simultaneously providing relative axial movement between the bit
and a form machining tool and rotating the tool relative to the bit
about the longitudinal axis of the latter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation, partly in section, of a rotary tool
which includes a wrapping bit in accordance with the present
invention.
FIG. 2 is a transverse end view of the conductor-wrapping bit of
the present invention.
FIG. 3 is a section view taken along the line 3--3 of FIG. 2.
FIG. 4 is a longitudinal section view taken along the line 4--4 of
FIG. 2 with a terminal in position and illustrating how the
helical-camming surface supports a wire convolution.
FIG. 5 is a partial longitudinal section view of the wrapping bit
illustrating how the wire-camming surface compensates for
variations in terminal dimensions.
FIG. 6 is a transverse end view of the wrapping bit in the process
of wrapping a conductor wire about a square terminal.
FIG. 7 is a section view taken along the line 7--7 of FIG. 6.
FIG. 8 is a section view taken along the line 8--8 of FIG. 2 and
showing a form machining tool in position to form the bit camming
surface.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is operable to be used in a variety of tools
commonly used in the art of making solderless wrapped electrical
connections including hand-held tools and automatic machines. A
typical hand-held or portable conductor wire wrapping tool is
illustrated in FIG. 1 and generally designated by the numeral 10.
The tool 10 includes a casing 12 and a handle 14. The casing 12
houses a suitable motor which is operated by depressing the
operator trigger 16. The forward end of the tool comprises a sleeve
18 attached to the front of the casing 12 and secured thereto by a
nut 20. The sleeve 18 includes a stationary collet and nut assembly
22 which is operable to removably secure an elongated tubular
sleeve element 24. The tubular sleeve 24 is operable to axially
retain and rotatably journal a conductor wrapping bit 26 preferably
made of heat treatable steel and having a bit end face 28 opening
to the distal end of the sleeve 24. The bit 26 includes an integral
shank 30 having a portion nonrotatably engaged with a rotatable
spindle 32 by means of a transverse pin 34. The spindle 32 is
suitably rotatably driven by the tool motor whereby the bit 26 is
rotated within the stationary supporting sleeve 24. In a manner
well known, the conductor wire wrapping bit 26 is operable to
tightly wrap the stripped end of a flexible electrical conductor
wire about a metallic post or terminal in a series of helical
convolutions to form a solderless electrical connection. The
particular geometry of the bit end face and surfaces in proximity
thereto which comprise an improvement in the art of wire-wrapping
bits is set forth herein.
Referring to FIG. 2, a central cylindrical bore 36 opens to the
transverse end face 28 of the bit 26 and is operable to receive a
substantially square cross section terminal 38 (see FIG. 6) in
place therein. The bore 36 extends a sufficient depth into the bit
26 to receive enough length of the terminal to wrap a plurality of
convolutions of conductor wire thereon as will be described.
Disposed about the bore 36 and intersecting the bit end face 28 is
a conductor wire camming and support surface 40 which slopes
radially inwardly with respect to the longitudinal bit axis 42 from
the end face 28 to the intersection with the terminal-receiving
bore 36. As viewed in FIG. 2, the surface 40 is formed to have a
helical advance in a clockwise direction around the bore 36. That
is, a point at a constant radius from the longitudinal axis 42 of
the bit 26 and lying on the surface 40 would follow a helical path
with respect to said axis if rotated in a clockwise manner.
Also opening to the end face 28 is a conductor wire receiving
groove 44 comprising a rectangular slot 46 longitudinally formed
near the circumference of the bit and closed by the inner wall 48
of the stationary support sleeve 24 (FIG. 6). An enlarged circular
counterbore portion 50 of the wire-receiving groove 44 (see FIG. 7)
is provided for receiving a portion of conductor wire insulation if
it is desired to form a wrapped connection having an insulated
portion.
Referring to FIGS. 2 and 3, the bit 26 is further provided with
wire-guiding surface means 52 intersecting the wire-camming surface
40 and the wire-receiving groove 44. The guiding surface 52 slopes
axially with respect to the longitudinal bit axis 42 (FIG. 3) from
the intersection with the camming surface 40 to the groove 44. As
may be seen in FIG. 3 the intersection of the surface 52 with the
groove 44 is formed by a radius R over which a conductor wire is
bent as it moves from the groove 44 along the surface 52 and into
the camming position at 54 on the camming surface 40. As shown in
FIGS. 2 and 3 the guide surface 52 is generally funnel-shaped
converging from the intersection with the groove 44 to the
intersection with the camming surface 40. The longitudinal axis of
the funnel-shaped surface 52 corresponds to the line 3--3 and lies
in a plane parallel to the longitudinal axis 42 of the bit. A
preferred method of forming the guide surface 52 is by means of a
rotary form milling cutter. Surrounding the conductor wire
receiving groove 44 is a somewhat U-shaped recess 58 which is
formed to facilitate a coining operation which forms the radius
R.
As previously mentioned, the operation of a conductor wire wrapping
bit is for the purpose of forming a series of contiguous
convolutions of wire wrapped tightly on a terminal. Superior
wrapped connections are performed by bits which cam the wire onto
the terminal rather than merely pulling the wire around the
terminal. Referring to FIGS. 6 and 7, the views show the terminal
38 wrapped with approximately two turns or convolutions of
conductor wire C. However, in commencing a wrapping operation, the
stripped end portion 60 of the conductor wire is inserted in the
groove 44 and the wire is laid in the notch 62 in the stationary
sleeve 24, see FIG. 6. Usually the insulated portion 64 of the wire
C extends just inside the notch as shown. The tool 10 is then
positioned over the terminal 38 with the terminal extending into
the bore 36 as shown in FIG. 7. With the wire C held stationary
relative to the sleeve 24 at the notch 62, the tool is operated to
rotate the bit 26 in the direction of the arrow in FIG. 6. At the
beginning of the wrapping operation the conductor wire is pulled
out of the groove 44 and guided by the funnel-shaped guide surface
52 to a position between the camming surface 40 and the corner 66
of the terminal 38, see FIG. 6, whereby the wire is cammed by the
surface 40 into contact with the terminal. As shown in FIG. 6,
there is actually penetration of the terminal corner 66 into the
wire C to assure adequate electrical contact area and a gastight
connection. Continued rotation of the bit 26 causes successive
portions of the camming surface 40 to come into camming and
supporting contact with the wire C to wrap a series of helical
convolutions.
A distinct advantage of the bit 26 is the provision of the
helically sloped camming and support surface 40 which compressively
embraces a major portion of a wire convolution whereby the wire is
continuously and substantially evenly pressed radially inward
against the terminal 38 and axially against the previous
convolution to provide a connection of superior mechanical and
electrical character. As can be seen in FIG. 4, by providing a
helical advance or lead to the camming surface 40 substantially
corresponding to the natural lead of a wire convolution 68 the
camming surface provides continuous and even force against the wire
as indicated by the force vectors 70 shown with their axial and
radial components. By providing support over a major portion of the
periphery of a wire convolution there is virtually no tendency for
the longitudinal bit axis 42 to wobble relative to the terminal 38
and hence no tendency to bend or deflect the terminal. This
reduction of unbalanced lateral forces between the bit and terminal
is enhanced by the coincident position of the terminal receiving
bore axis and the bit rotation axis 42.
A principal advantage of the bit 26 over known conductor wire
wrapping bits is illustrated in FIG. 5. The sloping cam surface 40
is operable to compensate for terminal diagonal dimensional
variations which affect the radial location of the terminal corners
66. If an undersize or lower dimensional limit terminal is
encountered, the conductor wire C is guided by the funnel-shaped
surface 52 onto the camming surface deeper in the recess formed by
the surface 40 or further away from the transverse end face 28
whereby it is properly cammed onto the edge 66. If a terminal 39,
designated by the dashed line, having the larger or maximum
diagonal dimension is encountered the conductor, represented by the
dashed circle, comes into camming position on the surface 40 closer
to the transverse end face 28. Compensation for dimensional
tolerances in wire diameter is also provided by the geometry of the
cam surface 40. Not only does the sloping cam surface 40 compensate
for wire and terminal dimensional variations, but the guide surface
52 provides for guiding the wire onto the camming surface at
various positions by permitting the wire to leave the funnel-shaped
surface at either a deep or shallow point with respect to the
convergence of the surface 52 with the camming surface 40.
The bit 26 is particularly advantageously used with wire diameter
of 0.010 inches or less wherein terminals have diagonal dimensions
of 0.030 inches or less. Tolerances encountered in manufacturing
terminals and conductor wire with these minuscule dimensions become
a significant portion of the total dimension, and it may be
appreciated from the foregoing that a bit in accordance with the
present invention operates to compensate for the imperfections of
mass produced terminals and wire.
As previously mentioned, the bit-camming surface 40 slopes radially
inwardly from intersection with the transverse end face 28 to
intersection with the longitudinal terminal-receiving bore 36 and
the surface 40 also has a helical rise with respect to the
longitudinal bit axis 42. Referring to FIG. 8, a preferred method
of forming the surface 40 is by means of a rotary form machining
tool 76. The tool 76 may be a milling cutter or a grinding tool or
any suitable tool on which a form surface 78 may be provided. The
tool 76 is rotatable about an axis 80 and is rotatably driven by
the shank portion 82 which is operative to be driven by a drive
spindle, not shown.
In the operation of forming the surface 40 on the bit 26, the tool
76 is positioned with its rotative axis 80 a predetermined radial
distance r from the bit longitudinal axis 42 and parallel thereto.
The tool 76 is then moved relatively toward the bit to penetrate
the end face 28 and form the deepest portion of the surface 40,
which is at the intersection of the surface 40 with the
funnel-shaped guide surface 52, see FIG. 2. With the tool 76
rotating about its axis 80, simultaneously, and at a constant rate,
the tool is rotated about the axis 42 with the axis 80 at the
radial distance r and axially is moved with respect to the end face
28 to form the surface 40 having a helical lead corresponding to
the natural lead of a wire convolution. Reversely, the bit may be
orbited around the axis 80 of the tool and moved axially with
respect to the tool-machining surface 78 to form the surface 40 the
result in either process being to effect relative motion between
the bit and the tool which will generate the sloped helical
surface.
* * * * *