Adjustable length slotless female contact for connectors

A connector having a center conductor contact whose length relative to an enclosing outer conductor contact can be adjusted to make a shoulder of the center conductor contact flush with the end of the outer conductor contact. In a female version of the connector, a cylindrical shell encloses a cavity in which a collette is inserted. An opening in a first end of the shell enables a male center pin to be inserted into the connector to make contact with the collette. The collette shape is such that the contacts between the collette and both the shell and the center pin are substantially at the opening of the first end of the shell. A spring on the other end of the collette presses the collette against the shell to produce wiping contacts at the opening.

Description of the Preferred Embodiment 
In FIG. 3 is shown a male connector having an adjustable length center 
conductor contact 31 of beryllium-copper. On a first end of contact 31 is 
a reduced diameter center pin 32 that projects forward from a shoulder 33. 
On a second end of contact 31 opposite end 32 are a set of threads 34 by 
which contact 31 is attached to a center conductor 35 of a transmission 
line. Center conductor 35 has radius r.sub.1 and is centered within an 
outer conductor 36 having an inner radius r.sub.2. Contact 31 is centered 
inside of a hardened beryllium-copper outer conductor contact 37 by a 
plastic bead 38. Encircling the bead is a hardened beryllium-copper ring 
39. A set of holes 310 are formed into the bead to make the average 
dielectric constant of the bead more closely approximate air. At bead 38, 
the inner radius r.sub.3 of ring 39 and the radius r.sub.4 of contact 31 
are chosen to compensate for the step change in dielectric constant at the 
bead so that characteristic impedance Z.sub.c at the bead is the same as 
within the transmission line 
A stainless steel coupling nut 311 is attached to contact 37 by a stainless 
steel snap ring 312 The coupling nut contains a set of threads 313 for 
attachment to an associated female connector. A set of threads 314 are 
also included to enable adapters to be attached to coupling nut 311. 
At a shoulder 315, the inner radius of contact 37 is from r.sub.3 to the 
inner radius r.sub.2 of the transmission line. Between shoulder 315 and 
hardened beryllium-copper ring 39 are a soft copper washer 316 and a 
hardened beryllium-copper washer 317. The length of the inner conductor 
contact 31 is adjusted by a controlled amount of compression of soft 
copper washer 316. A set of threads 318 on contact 37 and a set of threads 
319 on the transmission line outer conductor 36 enable contact 37 to be 
threaded onto the transmission line be a controlled amount. As contact 37 
is threaded onto outer conductor 36, a first end 320 of conductor 36 
presses ring 39 against washer 317. This compresses soft copper washer 316 
by an amount determined by the number of turns that contact 37 is threaded 
onto conductor 36 The number of turns is selected to make shoulder 33 of 
inner conductor contact 31 flush with an end 321 of outer conductor 
contact 37. 
A notch 322 in the outside surface of copper washer 316 facilitates the 
compression of that washer As washer 316 is compressed, it is deformed 
into an indentation 323 in contact 37. On the inner side of washer 317 
facing washer 316 is a notch 324 that produces a knife edge 325 and a 
wider bump 326 on the side of washer 317. The knife edge ensures that good 
contact is made between washers 316 and 317 at their inner surfaces of 
radius r.sub.2. This assures that the current from outer conductor 36 can 
flow along the inner surface of ring 39 and then across the inner surfaces 
of washers 316 and 317 to the inner surface 327 of contact 37. The 
dimensions of washers 316 and 317 including the sizes of notch 322 and the 
width of bump 326 are selected so that the typical amount of force needed 
to crush washer 316 to make shoulder flush with end 321 is on the order of 
50% of the yield strength of threads 318 and 319. This assures that once 
the length is adjusted that this length will be retained under normal use 
of the connector. Although the connector shown in FIG. 3 is a male 
connector, the length of the inner conductor contact of a female connector 
or of a sexless connector can also be made adjustable in the same manner. 
In other embodiments, the malleable washer and the hard washer could be 
located between the bead and a shoulder on inner conductor contact 31. 
However, it is more advantageous to use a shoulder of outer contact 37 
because the shoulder can be larger there In the case in which a shoulder 
of the inner contact is used, the bead must have a hard inner ring in 
contact with the hard washer 
In FIG. 4 is shown a gauge suitable for use in adjusting the length of the 
inner conductor contact of connectors of the type shown in FIG. 3. This 
gauge has a pair of cylindrical sleeves 41 and 42 that are shown in ion. 
Sleeve 41 is rigid and has a shoulder 43 that sits against end 321 of the 
outer conductor contact 37. Sleeve 42 is movable and is coupled to a 
pointer 44 of the gauge. End 45 of sleeve 42 sits against shoulder 33 or 
center conductor contact 31 so that the position of pointer 44 indicates 
the position along an axis A of shoulder 33 relative to end 321 A portion 
46 of sleeve 41 has a length L substantially equal to the distance between 
shoulder 33 and the nearest edge of plastic bead 38 The radius of portion 
46 is slightly less than the inner diameter r.sub.2 of inner conductor 36 
so that portion 46 fits snugly within outer connector contact 37 As a 
result of this, when washer 316 is compressed, portion 46 prevents it from 
bulging inward toward center conductor contact 31. Therefore, a conductive 
path across washers 316 and 317 is produced at a radius substantially 
equal to the radius r.sub.2 of the inner surface of outer conductor 36. 
In FIG. 5 is shown an adjustable length slotless female connector. This 
connector has a shell 51 (shown in greater detail in FIG. 6) and a 
collette 52 (shown in greater detail in FIGS. 7A-7C) In FIGS. 6 and 7A-7C, 
the dimensions shown are in inches. In shell 51 is formed a cavity 530 
having three cylindrical sections 531-533 of successively decreasing 
radius. A shoulder 534 is formed at the boundary between sections 532 and 
533 Section 531 has an opening 535 at a first end of the shell. Near 
opening 535, the sidewall of the shell slopes inward (at an acute angle B 
relative to cylindrical axis A) forming a sloping inner wall 536 at which 
the collette is to make contact. By an acute angle, is meant that angle B 
is less than ninety degrees when this angle is measured from the portion 
of axis within cavity 530. A set of threads 54 are formed on a second end 
of the shell opposite to the first end. Threads 54 enable the shell to be 
screwed into the end of the center conductor of a transmission line. 
In FIG. 7A is an end view of the collette In FIG. 7B is a cross-sectional 
view and in FIG. 7C is a side view as indicated in FIG. 7A. A set of slots 
71 extend from a first end 72 of the collette up to a base 77 of the 
collette to form a set of six tines 73. The tines enclose a cavity 74 into 
which a center pin 32 of a male connector can be inserted. At end 72, each 
of the tines slopes inward forming a sloping outer wall 75 an acute angle 
C (as measured from the portion of axis A within the collette). In this 
embodiment, angle C is thirty degrees. This slope is greater than the 
slope of inner wall 536 of the shell so that when the collette is inserted 
into the shell, contact between the collette and the shell is made at tips 
76 of the tines. This assures that, even for center pins having a range of 
diameters, contact between the collette and the shell occurs within a few 
thousandths of an inch of opening 535, thereby producing a repeatable 
impedance at the interface between-a male and a female connector. 
A set of slots 78 are formed in the base to produce a spring 79. When the 
collette is inserted into the shell, a base 710 of the spring sits against 
shoulder 534 of the shell. When the collette is inserted into shell 51, 
spring 79 and the resilience of the tines cooperate to press the tips 76 
of tines 73 against sloping inner wall 536 of the shell. When the collette 
is inserted into shell 51, spring 79 enables the collette to move slightly 
further into cavity 74, thereby enabling tips 76 to spread apart to 
accommodate the center pin. This results in a wiping contact at the point 
of contact between the tips 76 and sloping wall 536. Because hole 535 will 
not let oversize or bent center pins into the shell, this protects the 
collette from damage by such center pins 
On the inside surface of the collette are a set of threads 711. This 
enables the collette to be replaced by inserting a threaded shaft through 
opening 535 and threading the shaft into threads 711. This enables the 
collette to be pulled out of the shell through opening 535 so that it can 
be replaced by another collette. In FIG. 8 is an alternate embodiment of 
the slotless female center conductor contact. In that embodiment, all 
parts other than a cylindrical shell 81 are formed as one unitary part. 
This unitary part is inserted into shell 81 through a hole 839 in the back 
end 841 of shell 81 until a shoulder 840 of the unitary part is flush with 
an end 841 of shell 81. A ring 850 of solder is melted to rigidly couple 
the unitary part to shell 81. A set of threads 851 are included to connect 
this center connector contact to the center conductor of a transmission 
line. Because hole 839 is larger than the hole 852 through which a male 
center pin is to be inserted into this female connector, the unitary part 
can have a larger diameter than if it had to be inserted through hole 852 
as is done for the embodiment in FIG. 5. This design is therefore useful 
for manufacturing smaller and/or cheaper center conductor contacts than 
the contacts of the type in FIG. 5 
In FIG. 9 is shown the male connector of FIG. 3 mated to the slotless 
female connector of FIG. 5. A small gap 91 is shown between shoulder 33 of 
male center conductor contact 31 and end 53 of female center conductor 
contact 51. Except for this small gap, the characteristic impedance is 
constant clear across both connectors. When the center conductor contact 
of both the male and female connectors are adjusted to be flush, this gap 
will substantially vanish. Even in the case of a small gap, for the 
relatively high frequencies typically transmitted across these connectors, 
the capacitance across the gap substantially shorts end 53 of the female 
connector to shoulder 33 of the male connector, thereby decreasing the 
effect of the gap. Thus, the combination of the slotless female contact 
and the adjustability of the length of the center conductor contact for 
both connectors produces a constant and calculable characteristic 
impedance over substantially the entire length of both connectors, thereby 
significantly reducing reflections and resonances that would otherwise 
arise.