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Description  |
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FIELD OF THE INVENTION
The present invention is related to a machine for positioning and
assembling an electrical connector to the edge of a printed circuit board
and in particular to a machine that, during such assembly, compensates for
the thickness of the board that varies from board to board.
BACKGROUND OF THE INVENTION
In certain high density circuit board applications such as board to board
interconnections one of the mating connectors is attached to the edge of
one of the boards and the other connector is either attached to the edge
or on the surface of the other board. Such connectors, when mounted to the
edge of the board, occupy less board space than their surface mount
counterparts, and therefore are more desirable in these applications.
Examples of these types of connectors are disclosed in U.S. Pat. Nos.
5,199,885 and 5,127,839 which issued to Korsunsky et al. on Apr. 6, 1993
and Jul. 7, 1992 respectively. As the circuitry on these circuit boards
becomes more dense the edge mounted connector must become correspondingly
smaller resulting in very delicate contacts. Any variation in alignment
during assembly of the connector to the circuit board may cause the
contacts to become damaged. Therefore, precise alignment is necessary.
However, variations in the thickness of the circuit board due to allowable
manufacturing dimensional tolerances make it difficult to consistently and
accurately align a high density edge mounted connector with the edge of
the board. This is especially the case where the connector includes
contacts that must be connected to circuitry on both sides of the board.
What is needed is an assembly machine having the ability to sense the
actual thickness of the circuit board and align the connector so that the
centerline between the opposing contacts is substantially coincident with
the actual center plane of the circuit board during assembly. This will
effectively split the difference in board thickness variation between the
two rows of opposing contacts, thereby reducing the chance of damaging the
contacts. The present invention is directed to this capability.
SUMMARY OF THE INVENTION
A machine is disclosed for positioning an electrical connector with respect
to the edge of a circuit board for electrical and mechanical attachment of
leads of the connector to circuitry on a major surface of the circuit
board. The circuit board defines a plane that intersects the center of the
edge and is substantially parallel with the major surface. The machine
includes a frame, means attached to the frame for receiving the circuit
board and positioning the major surface and the edge with respect to the
frame, sensing means for sensing the thickness of the circuit board, and
alignment means coupled to the frame and responsive to the sensing means
for positioning the connector in a first position in alignment with the
plane. Advancing means is provided for moving the connector from the first
position along the plane and in alignment therewith to a second position
wherein the leads of the connector arc in engagement with the circuitry on
the circuit board. The means for receiving the circuit board may be a
fixture precisely positionable on a ledge forwardly of the
connector-applying region of the machine and include an upper surface
shaped to complement the bottom surface of a particular card, and thus be
customized.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is an isometric view of an electrical connector and circuit board of
the type to be assembled together by the machine of the present invention;
FIG. 2 is an isometric view of a machine incorporating the teachings of the
present invention;
FIG. 3 is a plan view of the frame and link assembly of the machine shown
in FIG. 2;
FIG. 4 is a cross-sectional view taken along the lines 4--4 in FIG. 3 and
also showing a fixture and a circuit board in position for application of
a connector;
FIG. 5 is an end view of the assembly shown in FIG. 3;
FIG. 6 is a plan view of the carriage assembly of the machine shown in FIG.
2;
FIG. 7 is a cross-sectional view taken along the lines 7--7 in FIG. 6;
FIG. 8 is an end view of the assembly shown in FIG. 6;
FIG. 9 is a partial cross-sectional view taken along the lines 9--9 in FIG.
6;
FIG. 10 is a front view of the connector holder assembly of the machine
shown in FIG. 2;
FIGS. 11 and 12 are end and plan views of the assembly shown in FIG. 10;
FIG. 13 is a plan view of a detente plate that attaches to the assembly
shown in FIG. 10; and
FIG. 14 is an enlarged partial elevation view of the pusher plate-receiving
region 14--14 of the connector holder assembly of FIG. 10, showing the
detente plate of FIG. 13 in position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
There is shown in FIG. 1 an edge mount electrical connector 10 and a
circuit board 12 to which the connector is to be attached. The circuit
board 12 has two substantially parallel major surfaces 14 and 16 and an
edge 18 defining a perpendicular edge surface. Metalized circuitry (not
shown) is arranged on each of the major surfaces and terminates in either
one of the several contact pads 22 or one of the several plated through
holes 24. The plated through holes 24 are usually connected to ground. An
opening 26 is formed in the edge 18 in alignment with and intersecting
each hole 24. The connector 10 includes a housing 28 having a ground bus
30 extending along its longitudinal center with ground posts 32 projecting
through and outwardly of the housing, and a row of upper contacts 34 and a
row of lower contacts 36 on either side of the ground bus 30 having leads
or solder tails 38,40 respectively. Opposing solder tails 38,40 are spaced
slightly closer together than the thickness of the board but with angled
free ends so that when the connector is moved toward the board along the
dashed lines 42, the free ends of the contacts engage the edges of the
board and cam outwardly then slide along the surfaces of the board until
they electrically engage their respective contact pads 22. Additionally,
as the connector is being moved toward the edge of the board, the ground
posts 32 enter their respective openings 26 and engage and enter the
plated through holes 24. After assembly the unit is then subjected to a
soldering operation where each of the posts 32 and solder tails 38,40 are
soldered to their respective plated through holes 24 or solder pads 22.
The contacts 34 and 36, in the present example, are on 0.025 inch spacing
resulting in very small delicate structures. It is therefore necessary to
very precisely align the connector 10 and its two rows of solder tails 38
and 40 with the actual center of the edge 18. That is, a plane 44, shown
in phantom lines in FIG. 1, that is parallel with and centered between the
two major surfaces 14 and 16 and extending outwardly through the center of
the edge 18, must pass between the two rows of tails so that the opposing
pairs of tails 38 and 40 are equidistant from the plane. The machine of
the present invention, that will now be described, will sense the
thickness of the circuit board 12, determine the location of the plane 44,
accurately position the connector 10 with respect to the plane, and
assemble the connector to the circuit board.
There is shown in FIG. 2 a machine 50 having a frame and link assembly 52,
a carriage assembly 54, and a connector holder assembly or module 56. The
frame and link assembly 52, as best seen in FIGS. 3, 4, and 5 includes a
base plate 58 supported by left and right side rails 60 and 62
respectively. The base plate 58 seats in a pair of slots 64 formed in the
side rails and is secured in place by the screws 66. Each of side rails 60
and 62 has two cutouts formed therein, a rear cutout 68 and a forward
cutout 70 for receiving coupling links 72 and 74 respectively. Each
coupling link is pivotally attached to its respective side rail within the
cutouts by means of a shoulder screw 76 and has a pin 78 spaced from and
axially parallel with the shoulder screw and projecting toward the
interior of the assembly for attachment to the carriage assembly, as will
be explained below.
A sensing means of the machine is coupled to connector holder assembly 56.
The pins 78 are pivotally journaled in their respective coupling links 72
and 74. Each of the links 74 includes an extension 80 that projects beyond
the end of its respective rail 60, 62 as shown in FIGS. 3 and 4. A sensor
bar 82 is attached to the ends of the two extensions 80 by means of the
screws 84 as shown. A pair of spaced sensor pins 86 are pressed into holes
in the sensor bar 82 and extend downwardly toward the base plate 58 for a
purpose that will be explained. Base plate 58 has a cutout 88 for
clearance for the connector holder assembly 56 and extends beyond the ends
of the side rails 60 and 62 to provide a mounting surface or ledge 90 for
supporting and holding tooling 280 that positions and holds the circuit
board 12 during assembly of the connector 10 to the board (in phantom in
FIG. 4).
A pair of L-shaped pillow blocks 92 are seated in shallow slots 94 formed
in the upper surfaces of the side rails 60 and 62 and secured in place by
means of the screw 96. A shaft 98 is journaled for rotation in the pillow
blocks 92. A pair of crank arms 100 are secured to the shaft 98 by means
of the set screws 102 tightened against flats on the shaft. The crank arms
are spaced adjacent each pillow block so that all appreciable end play of
the shaft is removed. Each crank arm 100 has a crank pin 104 pressed into
a hole in the end of the arm so that the two pins extend toward each other
as shown in FIG. 3. Each crank pin has a groove 106 for receiving a
retaining ring for a purpose that will be explained. The shaft 98 extends
beyond the pillow blocks 92 on both sides of the carriage assembly for
mounting a handle 108 on either side, as desired. The handle includes a
shank 110 that is threaded into a hole in a collar 112 and secured to the
shaft by means of a set screw 114. The handle 108 is used to manually
operate the machine as will be described below.
The carriage assembly 54, as best seen in FIGS. 6, 7, 8, and 9 includes a
carriage plate 120 having a top surface 122 and a bottom surface 124. A
first recess 126 is formed in the surface 122 and a second recess 128 is
formed in the floor of the first recess, both recesses being parallel with
the sides of the carriage plate 120. Four elongated holes 130 are formed
through the floor of the first recess, extending completely through the
carriage plate. Four slots 132 are formed in the top surface 122, each
slot including a wedge member 134 that is secured in one end of the slot
by means of a screw 136. The angled surface of the wedge faces the other
end of the slot thereby defining a cavity 138 for receiving one of the
pins 78 that project from the links 72 and 74. To assemble the carriage
plate 120 to the frame and link assembly 52, the wedges 134 are removed,
the carriage plate positioned between the side rails 60 and 62, and the
carriage plate lowered until the pins 78 enter the slots 132. The wedges
are replaced and the screws 136 are then tightened causing the angled
surfaces of the wedges to engage the pins 78, locking them in place within
the cavities 138.
The side rails 60 and 62 of the frame, the links 72 and 74, and the
carriage plate 120 form a four bar linkage where the carriage plate 120
may pivot about the shoulder screws 76 while remaining parallel with the
surface 90 of the base plate 58. As the carriage plate so pivots, the
sensing bar 82 moves toward or away from the surface 90 along a path that
is substantially normal to the surface, although the path is arcuate. This
is because the angle that the two pivot points of each of the links makes
with the surface 90 is only about 10 degrees or less. A slide member 140
is arranged to slide back and forth within the recess 126 of the carriage
plate 120 along a centerline 142 that is parallel with the surface 90. The
slide member 140 includes a follower rail 144 extending forward along each
side thereof in a direction parallel with the centerline 142. A cam
follower pin 146 is positioned near the free end of each of the rails 144,
having a reduced diameter shank that is journaled for rotation in a hole
in the rail for a purpose that will be explained.
The carriage plate 120 includes a pair of spaced slots 148 formed in the
bottom surface 124 that are parallel with the centerline 142. Each of the
slots 148 loosely receives a rail 150 which has a lower follower rail 152
extending forward along the outside edge thereof, directly under and in
alignment with the follower rails 144. The free ends of the lower follower
rails 152 each have a cam follower pin 146 which is journaled for rotation
in a hole therein in alignment with the cam follower pins in the follower
rails 144. The rails 150 are attached to opposite sides of the slide
member 140 by four screws 154 and four spacers 156 that extend through the
elongated holes 130. The spacers 156 are slightly longer than the
thickness of the carriage plate 120, at that point, so that the slide
member and the rails 150 are free to slide back and forth within the
recess 126 and within the limits of the elongated holes 130. The carriage
plate 120 includes a left forward projecting portion 158 and a right
forward projecting portion 160 that form an opening 162 for receiving the
connector holding assembly 56 so that the cam follower pins 146 can
operationally engage cams thereon, as will be explained below. A left
clevis 164 and a right clevis 166, each having a pin 168 extending
therefrom, are seated in shallow recesses on opposite sides of the slide
member 140 and secured in place by means of the screws 170. The clevises
164 and 166 are positioned so that the two pins 168 are parallel and in
substantial alignment with a respective crank pin 104. A pair of levers
172, each having a hole at one end sized for a slip fit with the pin 168
and a hole at the other end sized for a slip fit with the crank pin 104,
interconnect the slide member 140 with the shaft 98 as shown in FIG. 2.
As the handle 108 is moved in the direction indicated by the arrow A in
FIG. 2, the crank arms 100 rotate upwardly causing the carriage assembly
54 to move downwardly toward the surface 90 as the links 72 and 74 pivot
about their respective shoulder screws 76 until the sensor pins 86 engage
the upper or first surface of the circuit board 12 which is on a fixture
mounted to the surface 90, shown in phantom lines in FIG. 4. At this point
the vertical position of the carriage assembly 54 is known with respect to
the upper surface of the board, and the position of the lower surface of
the board is also known since it is resting on a fixture of known height
from the surface 90. Therefore, the exact position of the center plane 44
of the circuit board 12 is known with respect to the machine 50. As
movement of the handle continues, the levers 172 cause the slide member
140 to slide within the recess 126 for a purpose that will be explained.
A connector pusher plate 174 is located in a pair of slots 176 formed in
the under surface of the slide member 140, as best seen in FIGS. 6, 7, and
8. The pusher plate 174 is attached to the slide member 140 by the screws
178 and the dowel pins 180 so that the pusher plate is carried by the
slide member. The leading edge 182 of the pusher plate 174 is configured
to engage an inside surface of the housing of the connector 10 (FIG. 1)
and an edge of the ground bus 30 so that adequate support is provided when
the pusher plate pushes the connector into position on the circuit board,
as will be further explained below.
The connector holder assembly 56, as shown in FIGS. 10, 11, and 12,
includes a vertical support plate 200 having a left flange 202 and a right
flange 204 on opposite ends (FIG. 12). Each flange has a horizontally
disposed slot 206 formed therein and sized to be a close slip fit with the
left and right portions 158 and 160 respectively, of the carriage plate
120. This allows the plate 200 to freely slide back and forth with respect
to the carriage plate 120 in the direction of the centerline 142. An
elongated opening 208 is horizontally disposed through the plate 200, in
alignment with the pusher plate 174, and sized so that the end 182 of the
pusher plate (FIG. 7) can extend therethrough with little clearance along
the bottom surface of the opening.
A recess 210 is formed in the lower surface of the opening 208 and sized to
loosely receive a detente plate 212, as best seen in FIG. 14, the detente
plate being detailed in FIG. 13. The detente plate 212 is a relatively
thin rectangular member having a long slot 214 intersecting one end and
running most of the length of the member and terminating in a hole 216.
First and second detente openings 218 and 220 are formed in the walls of
the slot 214 as shown. A retainer pin hole 222 is formed in the end of the
plate 212 adjacent the hole 216. The plate 212 is made of a spring
material so that the two ends 224 and 226 will elastically spread apart
when a pin that is of the size of the opening 218 is forced into the end
of the slot 214. When the pin reaches the opening 218 the ends 224 and 226
will return to their rest position, holding the pin captive within the
opening. The opening 220, being of the same size as the opening 218, is
spaced therefrom by a specific amount and functions in a similar manner.
As shown in FIGS. 10 and 14 a retainer pin 228 is disposed in a hole
formed in the vertical support plate 200 so that it intersects the center
of the recess 210. The retainer pin extends into the hole 222, and since
the pusher plate 174 is directly above the lower surface of the opening
208, the detente plate 212 is effectively retained within the recess 210.
The purpose of the detente plate 212 will be explained below.
A pair of upper and lower U-shaped members 230 and 232 respectively are
arranged to slide freely toward and away from each other along the flange
202. A cam slot 234 that slopes upwardly to a horizontal slot 236 is
formed in the side of the U-shaped member 230 as best seen in FIG. 11. A
similar cam slot 238 that slopes downwardly to a horizontal slot 240 is
formed in the side of U-shaped member 232. These slots are sized to
receive the cam follower pins 146 with very little play. A retainer 242 is
attached by screw 245 to the edge of each of the U-shaped members adjacent
the cam slots to retain the follower pins within the cam slots. Similarly,
another pair of upper and lower U-shaped members 244 and 246 respectively,
are arranged to slide freely toward and away from each other on the flange
204. U-shaped members 244,246 have cam slots 234,238 and horizontal slots
236,240 respectively, and a retainer 242 and screw 245 adjacent each slot
in a manner similar to the U-shaped members 230 and 232. With the
connector holding assembly 56 in position within the opening 162 of the
carriage plate 120, the cam follower pins 146 are in operational
engagement with the cam slots 234 and 238 of each of the U-shaped members
230, 232, 244, and 246. As the slide member 140 is advanced, to the right,
as viewed in FIG. 6, the cam followers 146 riding in the cam slots 234 and
238 cause the U-shaped members of each pair to move toward each other
until the cam followers reach the horizontal slots 236 and 240 and the
U-shaped members are in their closed positions. At this point, as movement
of the slide member 140 continues, the U-shaped members remain in their
closed positions thereby providing a lost motion effect for a purpose that
will be explained.
The connector holding assembly 56 is coupled to the carriage plate 120 by
means of the detente plate 212. As is shown in FIG. 8, there is an opening
248 between the floor of the second recess 128 and the bottom of the
pusher plate 174. The detente plate 212 is disposed within this opening. A
pin 250 having a head is pressed into a hole formed in the bottom of the
recess 128 so that the head is within the opening 248. The head is
dimensioned to the same size as the openings 218 and 220 of the detente
plate 212, and will normally be in one of these openings.
Upper and lower combs 252 and 254 respectively, are attached to the edges
of the U-shaped members 230, 232, 244, and 246 by means of the screws 256
as shown in FIGS. 10, 11 and 12. The combs are carried with the U-shaped
members as they are moved back and forth between their open and closed
positions. In the open comb position, shown in FIGS. 10 and 11, the
opening 258 between their opposing edges is wide enough to permit passage
of a connector. In the closed comb position, however, the opening 258 will
not allow the housing of the connector to pass. A series of slots 260 are
formed in the opposing edges of the combs and are spaced to conform with
the spacing of the solder tails 38 and 40 of the connector 10 (FIG. 1).
The width of the slots 260 provide a small amount of clearance for the
solder tails so that they can be positioned in the slots. In the present
example, the entire solder tail is not received in the slot 260, but
rather a projection 262 formed on the outer edge of the solder tail, as
best seen in FIG. 1, is received in the slot. A lead in chamfer is
provided for each slot 260 to aid in the insertion. As best seen in FIG.
12, the comb 252 and the face of the vertical support plate 200 form a
cavity 264 for receiving a magazine, not shown, that dispenses the
connector 10. A pair of alignment blocks 266 and 268 having lower
shoulders 270 are rigidly attached to the face of the vertical support
plate 200 as shown in FIG. 12. The alignment blocks 266 and 268 are
arranged to accurately locate the connector magazine. With the magazine in
place the lowest connector in the magazine is positioned on the shoulders
270 thereby providing accurate vertical positioning.
OPERATION OF THE INVENTION
Referring now to FIGS. 2, 4 and 12, a magazine of connectors 10 is loaded
into the cavity 264 and the first circuit board 12 is positioned on and
secured to a fixture 280, shown in FIGS. 2 and 4. Circuit board 12 is
placed on upper surface 282 of fixture 280 to be disposed upon a
board-receiving surface portion 284, with locating pins 286 extending
upwardly from surface portion 284 received into precisely complementary
holes 288 of board 12 for precision board placement during assembly (FIG.
4). Fixture 280 in turn is precisely positioned on the upper surface of
ledge 90 with locating posts 290 extending upwardly from ledge 90 received
into precisely complementary fixture holes 292 for accurate fixture
placement. Fixture 280 is customized to a particular circuit board 12,
with surface portion 284 being contoured or profiled to provide clearance
for any components which may be mounted to the bottom surface of circuit
board 12, all such that the bottom surface of circuit board 12 is disposed
at a precise angle with respect to the upper surface of ledge 90 (such as
preferably parallel). If desired, the board-receiving surface portion may
be defined in a board-receiving nest or pocket. With surface portion 284
being defined on fixture 280 a precisely controlled distance above the
bottom surface of the fixture, the bottom surface of circuit board 12 is
now precisely referenced to the machine of the present invention for
precise determination of the medial plane 44 and precise application of a
connector to the circuit board edge.
Referring to FIG. 2 in operation, the head of the pin 250 (FIG. 8) is
disposed in the opening 220 of the detente plate 212 (FIG. 13). The handle
108 is then pulled by the operator in the direction indicated by the arrow
A. As the shaft 98 begins to rotate the crank arms 100 cause the levers
172 to allow the carriage assembly 54 and the links 72 and 74 to pivot
about their respective pivot points thereby causing the connector holder
assembly 56 to move downwardly toward the surface 90. This downward
movement continues until the sensor pins 86 engage the upper major surface
14 of the circuit board 12. At this point the centerline of the connector
10 that is positioned on the shoulders 270 is coincident with the center
plane 44 of the circuit board 12. Further movement of the handle 108 in
the direction of the arrow A causes the levers 172 to push the slide
member 140 in a direction that is parallel with the plane 44 and generally
toward the circuit board 12. At the beginning of this movement of the
slide member 140 the follower pins 146 engage the cam slots 234 and 238 in
the U-shaped members 230, 234, 244, and 246 causing the U-shaped members
to move toward the plane 44 to their closed position where the follower
pins are just entering the horizontal slots 236 and 240. The connector
holder assembly is prevented from moving by the head of the pin 250 being
in the opening 220 of the detente plate 212. As movement of the handle
continues, the leading edge 182 of the pusher plate 174 engages surfaces
on the inside of the housing and the center ground contacts 30 of the
connector 12 thereby pushing the connector 10 toward the circuit board 12.
As the connector moves toward the circuit board the follower pins 146 move
in the horizontal slots 236 and 240 maintaining the combs in their closed
position and the projections 262 on each of the solder tails 38 and 40
enter respective slots 260 in the combs 252 and 254 until the housing of
the connector 10 abuts against the inside face 272 of the combs and begins
pushing the combs and the entire connector holding assembly 56 toward the
circuit board 12. Since the connector detente plate 212 is pinned to the
vertical support plate 200, it moves along with the connector holding
assembly 56 causing the ends 224 and 226 to spread apart as the head of
the pin 250 slips out of the opening 220. Immediately thereafter the tips
of the solder tails engage the edge 18 of the circuit board 12, the lead
in portion of the tails in the row 38 camming up to the major surface 14
and the angled free ends of the tails in the row 40 camming down to the
major surface 16 while the slots 260 maintain the delicate solder tails in
alignment and prevent them from bending or deflecting.
As the connector 10 continues to move toward the circuit board 12, the
ground posts 32 enter into the openings 26 in the edge of the circuit
board 12 and engage and enter the plated through holes 24, at the same
time the solder tails 38 and 40 engage their respective solder pads 22 on
the board 12. At this point the handle 108 is fully forward, the head of
the pin 250 is in the opening 218 of the detente plate 212, and the
connector 10 is assembled to the circuit board 12 and ready for soldering.
The frictional engagement of the ground posts 32 in their respective
openings 26 and the solder tails 38 and 40 pressing against the solder
pads 22 on each side of the circuit board is sufficient to hold the
connector in place on the board until soldering. Note that all of the
sequential movements of the machine elements described above were
accomplished by a single motion of the handle 108 in the direction of the
arrow A. The handle 108 is then moved in a direction opposite that of the
arrow A which causes the slide member 140 to move to the left, as viewed
in FIG. 6, thereby retracting the pusher 174 away from the connector 10,
the follower pins 146 then engaging the cam slots 234 and 238 causing the
U-shaped members 230, 234, 244, and 246 to move apart thereby moving the
combs 252 and 254 apart to their open position as shown in FIG. 10. While
this is occurring the connector holder assembly is held stationary with
respect to the carriage plate 120 by the head of the pin 250 being in the
opening 218. When the follower pins engage the retainers 242, the entire
connector holder assembly 56 is now pulled along with the slide member 140
until it is clear of the connector 10 and board 12. This causes the
detente plate 212 to move with respect to the pin 250 so that the head of
the pin is forced out of the opening 218 and into the opening 220 again.
The connector and board assembly is then removed and a new circuit board
12 is secured in place in the fixture 272 and the process repeated.
An important advantage of the present invention is that a single operator
effected motion of the handle caused the several functional motions of the
elements of the machine. Another important advantage is that the actual
thickness of the circuit board is sensed and the center of the connector
is automatically adjusted to correspond with the center of the board,
thereby tolerating a wide variation from the nominal dimension of the
thickness of the circuit board.
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