Snap action removable knob

A knob assembly is provided which includes a knob having an integral shaft. The knob further includes a circular groove therein, and first and second cams situated in the groove. A knob receiving member includes an aperture in which the shaft of the knob is situated. Two snap fingers of flexible material extend from the sides of the aperture to engage the knob when the knob is pressed into the aperture. The knob is conveniently removed from the aperture by rotating the knob until the first and second cams contact and push the first and second snap fingers, respectively, out of the groove.

BACKGROUND OF THE INVENTION 
This invention relates to rotatable knobs and, more particularly to a snap 
action rotatable knob which is easily removed from a knob receiving member 
into which the knob is positioned. 
DESCRIPTION OF THE PRIOR ART 
Conventional rotating knobs for electronic and other devices are typically 
mounted on a shaft protruding through a front panel of such devices. The 
knob is typically held to the shaft by a set screw, a retaining clip or 
other similar retaining apparatus. Although such knobs are removable from 
the shafts on which they are situated, additional tools such as screw 
drivers, allen wrenches, and the like must often be employed to achieve 
removal. Moreover, conventional knob-shaft assemblies are limited in that 
they employ a separate shaft to transfer rotational force from one side of 
a knob receiving member or panel to the remaining side of the panel. When 
such conventional shafts are to be removed from the panel, it is necessary 
to gain access to the back side of the panel. 
One object of the present invention is to provide a rotating knob which 
includes an integral shaft which may be removed from the knob receiving 
member from the front panel side without the need for gaining access to 
the back of the panel. 
Another object of the present invention is to provide a rotating knob which 
requires no setscrews, retaining clips or other non-integral retaining 
devices to achieve knob mounted and knob removal. 
Yet another object of the invention is to provide a rotating knob which 
requires no tools for removal. 
These and other objects of the invention will become apparent to those 
skilled in the art upon consideration of the following description of the 
invention. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is directed to providing a rotating knob which 
includes an integral shaft, the knob and shaft being removable from the 
front side of a knob receiving member without the use of any additional 
tools. 
In accordance with one embodiment of the invention, a knob assembly 
includes a knob having a substantially cylindroidal shaft portion with a 
substantially circular groove therein. The knob includes first and second 
cams situated spaced apart in the groove by a predetermined angle 
therebetween. The knob assembly further includes a knob receiving member 
having upper and lower opposed surfaces. An aperture is situated in the 
knob receiving member for receiving the shaft of the knob therein. The 
knob receiving member includes first and second flexible engaging members 
situated extending into the aperture so as to engage the groove of the 
knob when the shaft portion of the knob is inserted in the aperture. The 
first and second engaging members are situated spaced apart in the 
aperture by an angle therebetween substantially equal to the predetermined 
angle. Thus, the knob is removable from the knob receiving member when the 
knob is appropriately rotated such that the first and second cams contact 
and push the first and second engaging members, respectively, out of said 
groove. 
The features of the invention believed to be novel are set forth with 
particularity in the appended claims. The invention itself, both as to 
organization and method of operation, together with further objects and 
advantages thereof, may best be understood by reference to the following 
description taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates one embodiment of the knob assembly of the present 
invention. The knob assembly includes a rotary knob 10 fabricated from a 
relatively rigid material. For example, plastics, metals, and the like may 
be employed to fabricate knob 10 as long as the particular material 
selected exhibits sufficient structural integrity to push apart the later 
described snap fingers 22 and 24 when knob removal is desired. The 
removability feature of knob 10 is discussed later in more detail. 
In this embodiment of the invention, knob 10 includes a circular disk 11 
having upper and lower opposed surfaces, 11A and 11B, respectively. A 
raised ridge 12 is situated running across upper knob surface 11A to 
facilitate grasping knob 10 by hand. Knob 10 includes a cylindroidal shaft 
13 centrally situated extending from lower kob surface 11B, as shown in 
FIG. 1. Shaft 13 is oriented substantially perpendicular to lower knob 
surface 11B. 
Knob receiving member 20 includes an aperture 26 exhibiting a sufficiently 
large diameter to receive shaft 13 therein. The diameter of shaft 13 is 
sufficiently large to produce a snug fit when knob 10 is situated within 
aperture 26, but not so large as to prevent ease of rotation of knob 10 
when so situated. 
A groove 14 is situated in shaft 13 around the circumference thereof, as 
shown in FIG. 1. An O-ring type gasket 15 is situated in groove 14 such 
that when knob 10 is pressed into aperture 26, gasket 15 provides a water 
seal against external undesired liquids to which the knob assembly of FIG. 
1 may be subjected. Knob 10 further includes a second groove 16 situated 
around the circumference of the lower most portion of shaft 13 as shown in 
FIG. 1. Cams 17 and 18 are situated in groove 16 approximately 180.degree. 
apart as measured with respect to each other and the center of knob 10 
which is located on knob axis 21 (center line 21) as shown in FIG. 2. In 
this embodiment of the invention, cams 17 and 18 are formed by tapering 
portions of groove 16 to rise to the external surface 23 (FIG. 2) of shaft 
13 at the cites selected for cams 17 and 18. When knob 10 is pressed into 
aperture 26 of knob receiving member 20, shaft 13 pushes fingers 22 and 24 
(later discussed) apart until fingers 22 and 24 engage and snap into 
groove 16. Knob 10 is thus retained in aperture 26. 
FIG. 2 is a cross section of the knob assembly of FIG. 1 along a section 
line 2--2. Knob 10 is shown in the working position with groove 16 being 
engaged by flexible snap fingers 22 and 24 which extended into aperture 26 
of knob receiving member 20. Opposed surfaces 20A and 20B are defined as 
the upper and lower surfaces of the portion of knob receiving member 20 at 
which knob 10 is located. Knob receiving member 20 is fabricated from a 
material which permits snap fingers 22 and 24 to flex and be subjected to 
stress without fracturing. For example, the flexible members which form 
these snap fingers 22 and 24 are fabricated from polycarbonates and other 
plastic materials. Other embodiments of the invention employ metallic 
flexible snap fingers. However, the preferred embodiment of the invention 
employs flexible plastic snap fingers 22 and 24 which are integral parts 
of knob receiving member 20. 
The section view of FIG. 2 shows cam 18 as a dotted line structure in the 
lower portion of knob 10. In this view, cam 18 is on the backside of the 
knob which is hidden from view. An indented portion 19 adjacent groove 16 
is shown on the bottom of knob 10 of FIG. 2. Indented portion 19 is 
employed to receive a drive member which may engage a switch or other 
member whose position is to be changed by rotary motion imparted to knob 
10. 
FIG. 3 is a sectional view of the knob assembly of FIG. 2 taken along 
section line 3--3. The view of FIG. 3 shows the knob assembly with knob 10 
being in the working position, as opposed to the removal position later 
depicted in FIG. 4. As seen in FIG. 3, flexible snap fingers 22 and 24 
extend from deeply recessed regions 32 and 34, respectively. Regions 32 
and 34 are recessed into lower receiving member surface 20B. In some 
embodiments of the invention, a more shallow region 36 is recessed into 
surface 20B surface 20B between recessed portions 32 and 34 as shown in 
FIG. 3. Region 36 is not essential. In the embodiment of the invention 
shown in FIG. 3, the knob assembly permits knob 10 to substantially freely 
rotate for approximately 80.degree.. That is, from the knob orientation at 
which cams 17 and 18 are vertically oriented, as in FIG. 3, knob 10 
rotates 40.degree. clockwise from the vertical until cam 17 contacts snap 
finger 22 and cam 18 contacts finger 24. Knob 10 is also permitted to 
rotate counterclockwise approximately 40.degree. from the vertical until 
cam 17 contacts snap finger 24 and cam 18 contacts snap finger 22. Thus, 
knob 10 is permitted to rotate approximately 80.degree. in the total. In 
the present embodiment of the invention, it is noted that cams 17 and 18 
are 180.degree. apart, and that snap fingers 22 and 24 are situated in 
receiving member 20 and oriented 180.degree. apart with respect to each 
other. The angle between cams 17 and 18 is substantially equal to the 
angle between fingers 22 and 24. It will be appreciated by those skilled 
in the art that changing the angle at which snap fingers 22 and 24 are 
located with respect to each other and similarly changing the angle at 
which the cams 17 and 18 are oriented will result in a change in the total 
amount of rotation which knob 10 is permitted. 
FIG. 4 shows the knob assembly of the present invention with knob 10 being 
oriented in the knob removal position. That is, knob 10 is rotated beyond 
the approximately 80.degree. of rotation which it is permitted in its 
working position until cams 17 and 18 contact and push apart snap fingers 
24 and 22, respectively. When snap fingers 22 and 24 are pushed away from 
aperture 26 in this manner, knob 10 is defined to be in the knob removal 
position. When knob 10 is oriented in such knob removal position, the snap 
fingers 22 and 24 no longer engage groove 16 to hold knob 10 within 
aperture 26. Thus, in the knob removal position, knob 10 is easily removed 
from aperture 26 by simply pulling knob 10 out of aperture 26. 
The foregoing describes a knob assembly which includes a knob having an 
integral shaft and which is capable of being mounted in an aperture 
without the use of set screws, clips, or other retaining members. 
Moreover, the knob of the present invention requires no tools for removal 
and may be removed from the front side of the panel or knob receiving 
member in which the knob is situated. 
While only certain preferred features of the invention have been shown by 
way of illustration, many modifications and changes will occur to those 
skilled in the art. It is, therefore, to be understood that the present 
claims are intended to cover all such modifications and changes as fall 
within the true spirit of the invention.