U.S. patent number 3,602,284 [Application Number 04/859,626] was granted by the patent office on 1971-08-31 for variable resistor screwshaft retainer.
This patent grant is currently assigned to Bourns, Inc.. Invention is credited to Raymond T. Dion, Ronald E. Smith.
United States Patent |
3,602,284 |
Smith , et al. |
August 31, 1971 |
VARIABLE RESISTOR SCREWSHAFT RETAINER
Abstract
A potentiometer screwshaft-retaining structure in which the
screwshaft comprises an annular groove adjacent the shaft head
exterior of the potentiometer body, and a spring-wire clip having
end portions engaged in a recessed formation in the exterior
surface of the potentiometer body and engaging the screwshaft
around a major portion of the periphery thereof in the annular
groove and compressively engaging the body of the potentiometer to
hold the clip to the body and to prevent translation of the
screwshaft relative to the body.
Inventors: |
Smith; Ronald E. (Riverside,
CA), Dion; Raymond T. (Rialto, CA) |
Assignee: |
Bourns, Inc. (N/A)
|
Family
ID: |
25331364 |
Appl.
No.: |
04/859,626 |
Filed: |
September 22, 1969 |
Current U.S.
Class: |
411/352;
338/DIG.1; 338/180; 338/148; 411/999 |
Current CPC
Class: |
H01C
10/14 (20130101); F16B 39/26 (20130101); F16B
41/002 (20130101); Y10S 411/999 (20130101); Y10S
338/01 (20130101) |
Current International
Class: |
F16B
41/00 (20060101); H01C 10/00 (20060101); H01C
10/14 (20060101); F16B 39/26 (20060101); F16B
39/00 (20060101); F16b 043/00 () |
Field of
Search: |
;151/69,41.75,41.74
;85/1K,8.8 ;339/263,263B,263E,263L,272 ;338/148 ;16/38 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
26,684 |
|
Dec 1903 |
|
GB |
|
536,476 |
|
Jan 1957 |
|
CA |
|
Primary Examiner: Parsons, Jr.; Marion
Claims
We claim:
1. A variable resistor comprising
a resistor body having a bore receiving a rotatable actuating
screwshaft and a T-shaped recess in the body adjacent the bore,
said recess having a trunk portion parallel to said bore and slots
extending transversely from the trunk and said recess having
walls;
a screwshaft disposed in operative position in said bore and having
an annular groove disposed adjacent the outer end of said bore and
disposed generally transverse of the trunk portion of said recess;
and
a spring-wire screwshaft retainer disposed outside of said body and
having an intermediate arcuate portion engaging said screwshaft in
the annular groove therein and having first and second doubly-bent
limbs each integral with said arcuate portion and extending away
therefrom to said recess and each having a reach portion disposed
in the trunk portion of said recess and each of said limbs having a
foot portion disposed in a respective one of said slots of said
recess and compressively engaging a respective one of said
walls,
whereby said retainer restrains said screwshaft against axial
translation relative to said body while permitting rotation thereof
and removal of the retainer and screwshaft from said body without
alteration of said body.
Description
BRIEF SUMMARY OF THE INVENTION
Background of the Invention
Screwshaft-actuated variable resistors, principally in the form of
adjustment potentiometers, employ as an actuating means a screw
shaft which, either in the form of a lead screw or of a worm screw,
is manually rotated to effect adjustment of the value of resistance
made effective between two terminals of the resistor. Various means
have heretofore been used to prevent endwise movement of the
screwshaft after it is assembled into the body of the resistor in
actuating engagement with the slider or gear of the
resistor-operating mechanism, whereby undesired change of
adjustment by axial movement of the shaft induced by vibration or
the like is avoided. The prior art means include drive pins
inserted in a hole drilled in the body and seated in an annular
groove formed in the shaft, U-shaped retainer clips which are
devised to straddle the screwshaft and seat in a groove therein and
in a slot formed in the resistor body. All of such prior art
devices are expensive to install, and require precision
construction of the mating surfaces if axial translation of the
screwshaft is to be reduced to an acceptable or minimum value.
Additionally, such means require either destruction of the resistor
body, or removal of the resistor cover, or extremely careful and
delicate mechanical manipulation, for removal of the screwshaft
after completion of assembly of the resistor,
Brief Description of the Present Invention
The noted undesirable features of prior art resistor screwshaft
retainer schemes and means are avoided by the present invention by
the provision of a wire-spring-retainer device which when in use is
on the exterior of the resistor body and is under tension and thus
holds itself affixed to the resistor body while permitting easy
removal; and which is inexpensive to manufacture and to install and
which by virtue of spring tension insures against undesired
translation of the screwshaft while adding the bonus feature of
providing a desired measure of countertorque to rotation of the
screwshaft and hence serving as an automatic lock to prevent
undesired rotation of the shaft due to vibration of the resistor.
The wire spring retainer is in the form of a clip having two
resilient shaped limbs or end portions each integral with an
arcuate shaft-engaging portion disposed intermediate the end
portions. The limbs are shaped to be stressed toward each other
during installation of the retainer in a recess in the exterior of
the resistor body, and to expand away from each other and
compressively engage confining wall portions of the resistor body
with the arcuate intermediate portion of the clip diametrally
reduced and brought into snug engagement with the screwshaft.
The foregoing brief summary of the invention makes it evident that
it is a primary object of the invention to provide improvements in
screwshaft-retention methods and means for variable resistors.
Another object is to provide resistor-screwshaft-retaining means
which are readily applied to the resistor following assembly of the
body including any cover, and readily removable without disassembly
of the body. Another object of the invention is to provide a
screwshaft retainer for variable resistors, that is easily
adjustable to provide a desired brake effect on the screwshaft to
which it is applied. Other objects and advantages of the invention
are hereinafter set out or made evident in the appended claims and
the following detailed description of a principal and a subsidiary
embodiment of the invention.
An exemplary simple form of clip or retainer according to the
invention, and a more complex modified form, are illustrated in the
accompanying drawings, in which:
FIG. 1 is a pictorial representation to no specific scale of a
screwshaft-adjusted variable resistor, with the adjusting
screwshaft withdrawn from the resistor body and the spring wire
screwshaft retainer removed from the shaft, to show details;
FIG. 1a is a side view of the spring-wire screwshaft retainer shown
pictorially in FIG. 1;
FIG. 2 is a fragmentary view of an end face of the resistor
depicted in FIG. 1, showing the screwshaft and retainer in
place;
FIG. 3 is a view similar to FIG. 2, but with the screwshaft and
retainer removed;
FIG. 4 is a plan view of the screwshaft depicted in pictorial view
in FIG. 1;
FIG. 5 is a pictorial view of a screw-adjusted variable resistor in
the form of a potentiometer, utilizing a modified form of
spring-wire retainer according to the invention, with the
screwshaft and retainer disassembled and the screwshaft having
portions removed or broken away;
FIG. 6 is a fragmentary top view of a portion of the variable
resistor of FIG. 5, with the screwshaft and retainer in operative
positions; and
FIGS. 7 and 8 are top and end views, respectively, of the
screwshaft retainer shown in FIGS. 5 and 6.
DETAILED DESCRIPTION OF THE ILLUSTRATED STRUCTURES
In FIG. 1, a variable resistor in the form of a worm-screw-adjusted
potentiometer 10 is shown. The potentiometer comprises a box like
body 12 which provides a shaped internal chamber in which operating
components are disposed and which chamber is closed by a lid or
cover 14. The general arrangement of parts, except in respect of
the parts shown in the drawing, is conventional and may be, for
example, like or similar to that shown in one or another of U.S.
Pats. Nos. 3, 3,059,200; 200; 3,108,245; 3,127,583; and 3,150,343.
Mounting holes and terminal means are not herein shown since they
may be of various sorts and are not per se or in combination a part
of the present invention.
The body 12 of the resistor is of strong rigid material such as
thermoplastic or thermosetting synthetic resin. The cover 14 may be
of metal, or of strong cured polymeric material. The body is
provided with a screwshaft-receiving bore 16 for reception of the
shank 30s of the screwshaft 30. The body further has formed in the
end face adjacent and around the outer end of the bore, a shaped
recess 18. The lower portion of the recess is deep, and as is
indicated in FIG. 3, is of rectangular boxlike configuration. The
upper part of the recess is less deep and is bounded at the top by
a semicircular wall 18w.A shelf 18s forms a flat floor for the
upper portion of the recess, against which floor an annular flange
portion 30f of the screwshaft bears when the latter is in operating
position.
As shown in FIGS. 1 and 4, the screwshaft 30 has a threaded shank
30s , a transversely slotted head 30h the rearward end of which is
annularly grooved to provide the groove 30g and the flange 30f;
and, optionally, a reduced portion 30b is provided for reception of
an elliptical ring seal which is conventional and hence is not
shown.
The screwshaft 30 is adapted to be retained in operative position
in body 12 for rotation to adjust the resistor, and prevented from
axial translation, by the wire-spring clip or retainer 40. The clip
or retainer comprises first and second limbs 40r and 40s with
respective offsets 40m and 40n, both of which limbs are integral
with and join or merge with respective ends of an arcuate
intermediate portion 40a. The limbs as formed diverge as they
recede from the arcuate portion 40a, that is, they are spread
divergently apart when free. Thus the arcuate portion may be
readily mounted on the screwshaft at groove 30g where it is easily
rotated about the shaft axis. The offsets 40m and 40n position the
extremities of the limbs rearwardly of the plane of the arcuate
portion. Thus, with the clip mounted on the screwshaft, the latter
may be started into bore 16 and the limbs 40r, 40s forced toward
each other in a compressing action into a stressed configuration
indicated in FIG. 1, and the clip pressed into recess 18. By
pressing or forcing the limbs to the bottom or inner floor of
recess 18, the shaft is carried inwardly until flange 30f, presses
on the shelf 18s. Thereafter, upon release of the limbs, they tend
to spread apart due to the stress created when they were forced
toward each other; and as shown in FIG. 2, compressively engage the
sidewalls of recess 18 with sufficient force to prevent outward
translation of the screwshaft under action of any force to which it
is subjected in normal use. The clip 40, aided as may be by flange
30f, prevents further inward translation of the screwshaft.
For esthetic reasons, such as appearance and to preclude
accumulation of dust therein, and/or to make a more permanent
mounting of clip 40 to body 12, the otherwise unoccupied portion of
recess 18 can be filled with potting compound, embedding the limb
portions of the clip in recess 18.
In FIGS. 5, 6, 7 and 8 is illustrated a somewhat more complex form
of spring wire clip or retainer 50, and appurtenant cooperating
structural features including a grooved portion of a screwshaft 60
and a recess 12 r formed in body 12' of a variable resistor. The
clip comprises an arcuate intermediate portion 50a adapted to fit
in the groove 60g of the screwshaft, and two doubly-bent limbs 50r
and 50s comprising reaches 50t and 50u, respectively, and feet 50v
and 50w, respectively. As formed, the limbs are divergent, but may
be forced toward each other into a stressed configuration as shown
in FIGS. 5, 7 and 8. After application of the arcuate portion 50a
onto the screwshaft to seat in groove 60g, the limbs are compressed
or forced toward each other, and the screwshaft is pressed into
bore 16' of the resistor body 12' in a now evident manner. As the
flange 60f of the screwshaft approaches bore 16', the feet 50v and
50w strike inclines 12a and 12b formed on the body 12' , ride up
the inclines as the limbs resiliently flex, and ride over flats 12c
and 12d and snap down into slots 12e and 12f respectively, of the
T-shaped recess 12r formed as shown in the body. Thus the
next-adjacent reaches 50t and 50u of the limbs move into the trunk
of the T-shaped recess 12r, between the flats 12d and 12e; and when
the clip is released the limbs move away from each other and engage
the walls of the recess and firmly lock the screwshaft in position
as indicated in FIG. 6, with the feet 50v and 50w engaged in the
limbs of the T of the recess.
Removal of the clip for removal of the screwshaft without opening
the resistor body is readily accomplished by inserting a pointed
tool laterally into the bottoms of slot 12e and slot 12f and
lifting the feet over flats 12c and 12d while exerting withdrawing
force on the head of the screwshaft. As in the case of the
first-described embodiment of retainer, the otherwise unoccupied
portions of the slots and other portions of the recess 12r may, for
the noted reasons, be filled with potting compound. The latter is
not shown in the drawings in the interest of clarity of
illustration.
While in the particular embodiments shown in the drawings the
retainer clips are associated with variable resistors of the
worm-screw-adjusted potentiometer variety, it is evident that the
retainer clips described are equally applicable and useful in
connection with the lead screws of lead-screw-adjusted variable
resistors, since the housings or bodies of both varieties are made
of the same materials and by the same processes, and are of shapes
or configurations equally well adapted for provisions of the
clip-receiving recesses.
* * * * *