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Патент USA US2109674

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March 1, 1938.
J_ |_. McWEENY
Filed NOV. 26, 1937
Patented Mar. 1, 1938
John L. McWeeny, Chicago, Ill.
Application November 26, 1937, Serial No. 176,403
5 Claims. (Cl. 116—124.1)
My invention relates to radio receivers and par
ticularly to means intended for use to bring about by reference to the accompanying drawing, in
accurate indication of the tuning of such re
Fig. 1 is the side elevation of apparatus con
Many elements enter into the manufacture of structed in accordance with my invention;
Fig. 2 is a plan view thereof;
a radio chassis that tend to prevent any cer
Fig. 3 is a sectional view on the line 3-3 of
tainty in the matter of “capacity”, and this un
Fig. 2; and
certainty is increased where, as at present, many
Fig. 4 is a sectional View on the line 4-4 of
receiving sets are constructed to pick up fre
Fig. 3.
10 quencies over a wide range; in other words, so
In the drawing I have illustrated the essential
called all wave receivers.
This variation, notwithstanding the accuracy portions of a radio chassis including ~a base ID,
of machine-made products, occurs principally in a variable condenser ll, adjusted by a tuning
the condensers and although they are carefully knob l2 and having a shaft l3. Connected by
15 designed for a uniform minimum and maximum
capacity, it seems mechanically impossible to
produce exact duplicates, either throughout the
range or at individual points.
Furthermore, there is a known variation of ca
20 pacity from newto used conditions. Tempera
ture, bearing wear, the relieving of internal
stresses, etc., cause changes over a period of time.
The same remarks apply to the inductance ele
ments; temperature and moisture serve to cause
25 variations in the electric eifect which are re?ected
in the tuning of the instrument.
In the commercial production of radio receiv
ing sets, it is, from a practical standpoint, im
possible to individually calibrate each set in order
30 that the indicating means shall correspond ex
actly with the tuning means, practically all sets
being delivered from the assembly line with an
adjustment that is approximately correct but
gears id to the shaft l3 are a pair of cams l5—l6
mounted on a common shaft H. The cams are
constructed to provide lateral ?anges serving as 15
the active faces of the cams, the ?anges being
composed of a soft and readily bendable mate
rial. Thus the cam contours may be slightly
changed by the use of a pair of pliers or some
other suitable tool in order to compensate for
variations in the tuning indication. While I have
shown but two cams, one for each of two broad
cast bands, it will be understood that additional
cams may be provided for each band in the design
of the apparatus.
The indicating means may be any one of a
number of types, the one shown being merely a
pointer or ?nger I8 mounted for oscillation over
a dial I9. The pointer is carried by a shaft 20
that is splined as at 2| to permit the rearward
portion 22 to be reciprocated. A pair of pinions
23-24 are mounted on the shaft and are selec
which may in adjacent sets vary in the indication
tively engaged with the shaft through the spring
35 of the same station as much as 5 kc. and, as
lugs shown in Figs. 3 and 4. In other words, the
shaft 22 carries a pair of spaced plates 25-26
held apart by springs 21 and ?xed in position by
the cross pin 28. The pinions 23—24 are notched
as shown in Fig. 3 and the spring lugs are caused
above stated, after the passage of time, this Var
iation may be greater or less.
The correction of the indicating means as ap
0 plied to one broadcast band may be accomplished
with relative simplicity, but such corrections when
applied to another broadcast band would, un
fortunately, result in wide variations from ac
, curate indication. I have, therefore, provided
15 each broadcast band with an individual element
in the connection between the tuning device and
the indicator, each of said elements being capa
ble of adjustment for accurate calibration. Thus,
if desired in a more expensive set, each broad
;0 cast band may be separately and accurately cali
brated relative to a single indicating device. Fur
thermore, after the passage of time and the con
sequent readjustment of electrical values, the
calibrations may be corrected where required.
5 The invention will be more readily understood
to engage one or the other of the pinions by ax
ial movement of the shaft 22. This is brought
about through the bell crank 29 pivoted at 30 on
a bracket 3| and oscillated through a link 32,
rocker 33 and link 34, joined to the shaft 35
that operates the band switch 36. Thus, through
the medium of the knob 31 connected to the
shaft 35, the band switch may be shifted and, at
the same time, the pinion 23 or 24 is connected
to the shaft of the tuning indicator. Racks
38—39 are mounted for sliding movement in a
guide piece 40, the racks having rollers on their
ends that engage the active surfaces of the
?anges on the cams |5-—|6.
In the more inexpensive receiving sets, it may
be satisfactory to provide merely for correction
of the tuning of the main broadcast band in
tation therewith, the cam having a deformable
?ange constituting its active surface, whereby to
which case only one cam with its bendable ?ange
enable correction of individual frequencies.
will be provided. If, however, a plurality ‘of
bands are to be corrected as to their indications,
then a, plurality of cams and a suitable selecting
means should be provided as shown. By use of the
described apparatus, an accurate indication may
3. In radio receiving apparatus, the combina
tion of tuning means, indicating means and band
selecting means, a connection between the tuning
means and indicating means, a plurality of cams
in said connection, said cams having active sur
be secured at any time that the indication is in
faces capable of variation and means operated
correct, it being assumed, of course, that the by said band selecting means for selecting the 10
cam contour will be manufactured as closely as cam and connecting to the indicating means the
possible to the predicted capacity of the particu-' cam intended for use with the individual band.
lar design.
4. In combination, tuning means capable of
Wherever in the speci?cation and claims ref
variation to receive frequencies in different bands
erence is made to a cam having a bendable active
and indicating means, connections therebetween 15
effecting movement in unison, said connec
comprehend by such term any cam capable of tions including a plurality of cams adapted to be
being deformed or changed as to local points on selectively operatively connected, manually oper
its active surface.
ated means for selecting the cam corresponding
I claim:
to a particular band and means on said cams
1. In radio receiving apparatus the combina
permitting adjustment of local points on the
tion of tuning and indicating means, connections active surfaces whereby to enable correction of
including a rotatable cam between the tuning
and indicating means said cam having an in
variable connection to the tuning means for ro
25 tation therewith, the cam having its active sur
face capable of local variation whereby to cor
rect the indication of individual frequencies.
2. In radio receiving apparatus the combina
tion of tuning and indicating means, connections
30 including a rotatable cam between the tuning
cam having an in
and indicating means said
variable connection to the tuning means for ro
the indications transmitted thereby.
5. In combination, tuning means and indicat
ing means and connections therebetween, said 251
connections including a plurality of cams, racks
reciprocated by said cams, a shaft for operating
the indicating means, pinions on the shaft en
gaging said racks, a band switch and means op
erated by the band switch for selectively engag— 30
ing said pinions with said shaft.
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