Drive mechanism for picturn sign

A rotating sign assembly has a plurality of rotatable, multi-sided, sign segments and a drive mechanism for rotatably driving the sign segments. The drive mechanism includes a drive shaft and one or more output shafts that each operate to rotate a multi-sided sign segment. A cam is fitted to each of the output shafts so that rotation of the cam causes rotation of the corresponding output shaft and sign segment. The cam has an outer perimeter and multiple equally spaced engagement slots which extend radially inwardly from the outer perimeter. Outwardly facing stabilizing portions are positioned between each of the engagement slots. The cam has multiple dwell positions, each corresponding to the display of one side of the multi-sided sign segment operated by the corresponding output shaft. A cam driver assembly is fitted to the drive shaft so that it rotates with the drive shaft. The cam driver assembly has a cam driver which extends outwardly from the axis of rotation and terminates in a knob. The knob describes an arc as the cam driver is rotated about the axis of rotation. The cam driver is configured to engage one of the engagement slots when the cam is in a dwell position and to rotate the cam to another dwell position as the cam driver assembly is rotated about its axis of rotation. The cam driver assembly also includes a stabilizing member which is configured to engage one of the stabilizing portions of the cam when the cam is in a dwell position.

FIELD OF THE INVENTION 
The present invention relates generally to rotating sign assemblies and, 
more particularly, to a rotating sign assembly incorporating an output cam 
driven by a cam driver assembly to allow rotation of the output cam in set 
increments. 
BACKGROUND OF THE INVENTION 
Roadside signs have long been effective means for advertising and conveying 
messages. Known billboard style signs are advantageous in that they 
successfully advertise a message to a broad audience for a relatively low 
price. However, these signs suffer from a severe disadvantage in that 
their display message may be posted for weeks or months limiting their 
effectiveness over the long term. The viewing audience simply becomes 
bored with the same inanimate sign displaying the same message, and its 
marketing effectiveness drops off significantly over time. 
In response to conventional forms of billboard advertising, multi-sided, 
segmented, rotating signs were developed. These signs typically comprise a 
number of three-sided sign segments driven by a motor that selectively 
starts and stops or by a motor having some type of trip mechanism or 
clutch. One example of this type of sign is disclosed in U.S. Pat. No. 
3,387,394. 
The old approaches to multi-sided, segmented, rotating signs have several 
disadvantages. In order for the signs to properly display the message 
contained on one side of the segments, all of the segments must be 
precisely aligned. This requires that the mechanism controlling the 
position of the segments be precisely controlled. This can be accomplished 
by using some type of feedback position sensor that precisely controls the 
drive mechanism. However, this approach can be complex and costly and may 
require periodic adjustment or maintenance to maintain its proper 
operation. Therefore, there is a need for a drive mechanism that 
eliminates the need for such precise control and is simple, inexpensive, 
and durable. 
It is also desirable that the multi-sided segments be held securely in 
position while displaying each message. Gear and cam driven drive 
mechanisms often have slop or compliance that increases with wear. If slop 
or compliance develops in the system, the multiple segments may develop an 
uneven appearance detracting from the aesthetics and effectiveness of the 
sign. Therefore, it is desirable that a drive mechanism for a multi-sided, 
segmented, rotating sign include means to securely hold the segments in a 
display position between rotational movements. 
In traditional multi-sided, segmented, rotating sign assemblies, each of 
the segments rotates to a new display position at the same time. This 
creates the appearance of a quick and uniform fade from one advertising 
message to another. However, for some applications it is desirable that 
some of the sign segments rotate before other segments so that the 
appearance of a change sweeping from one portion of the sign to another 
can be created. Therefore, there is a need for a simple system which 
allows for sequential rotation of sign segments so as to create enhanced 
visual effects. However, these enhanced visual effects may only be 
desirable with certain advertising messages. As different advertising is 
substituted on the various sides of the multi-sided sign, it may be 
desirable to change the sequentially changing sign to a traditional 
uniformly fading sign. Therefore it is desirable that a drive mechanism 
provide for adjustability so that the same sign can be changed from 
providing a uniform fade from one message to another to providing a 
sweeping fade. It is especially desirable that such changes or adjustments 
be possible in a simple manner for signs that are already installed, such 
as along a highway. 
SUMMARY OF THE INVENTION 
There is disclosed herein a rotating sign assembly which includes a 
plurality of rotatable, multi-sided, sign segments and a means for 
rotatably driving the plurality of sign segments. The driving means 
includes a drive shaft which is rotatable around a first axis of rotation 
and at least one output shaft which is rotatable about a second axis of 
rotation. The output shaft is operable to rotate one of the multi-sided 
sign segments. A cam is fitted to the output shaft so that it rotates 
about the second axis of rotation. The cam has an outer perimeter and 
multiple equally spaced engagement slots which extend radially inwardly 
from the outer perimeter of the cam. The cam also has outwardly facing 
stabilizing portions defined between each of the engagement slots. The cam 
has multiple dwell positions, each dwell position corresponding to display 
of one side of the multi-sided sign segment operated by the corresponding 
output shaft. A cam driver assembly is fitted to the drive shaft so that 
it rotates about the first axis of rotation. The cam driver assembly 
includes a cam driver which extends outwardly from the first axis of 
rotation and terminates in a knob. The knob describes an arc as the cam 
driver is rotated about the first axis of rotation. The cam driver is 
configured to engage one of the engagement slots of the cam when the cam 
is in one of the dwell positions and to rotate the cam to another dwell 
position as the cam driver assembly is rotated about the first axis of 
rotation. The cam driver assembly also includes a stabilizing member which 
is configured to engage one of the stabilizing portions of the cam when 
the cam is in a dwell position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a rotating sign assembly according to the present 
invention is generally illustrated at 10. The rotating sign assembly 10 
includes a plurality of rotatable, multi-sided, sign segments 12 arranged 
vertically side by side. In the preferred embodiment, each of the sign 
segments 12 has three sides joined together such that the sign segments 12 
have a triangular cross section. Each of the three sides of the sign 
segments 12 are decorated with a part of an advertising image. Referring 
to one side of each of the sign segments 12 as a first side, an 
advertising image is divided into multiple segments and one segment is 
placed on the first side of each sign segment 12. Then, when the multiple 
sign segments 12 are all rotated so that the first side is aligned so as 
to form an essentially continuous flat surface, the complete advertising 
image is displayed. As can be seen, a different advertising image can be 
divided among the segments on each of the three sides on the sign segments 
12. Then, starting with the sign segments 12 positioned so as to display 
the first advertising image, rotation each of the segments 120 degrees 
clockwise will cause the multiple sing segments 12 to once again align to 
display a second advertising image. Rotating the segments 12 an additional 
120 degrees will display the third advertising image and rotating the 
segments yet again will once again display the first advertising image. 
As will be clear to one of skill in the art, successful operation of the 
rotating sign assembly 10 requires some type of driving mechanism capable 
of rotating all of the sign segments 12 from one display position to 
another display position. The drive mechanism according to the present 
invention includes a drive shaft 20 which is rotatable about a first axis 
of rotation 22 and multiple output shafts 24 which are each rotatable 
about an axis of rotation which is perpendicular to the first axis of 
rotation 22. The drive shaft 20 is rotatably driven about the first axis 
of rotation 22 by a motor (not shown). The output shafts 24 each drive a 
corresponding one of the sign segments 12. Therefore, rotation of an 
output shaft 24 causes rotation of the corresponding sign segment 12. A 
cam 30 is fitted to each of the output shafts 24 so that rotation of the 
cam 30 causes rotation of the corresponding output shaft 24 which causes 
rotation in the corresponding sign segment 12. In FIG. 1, the cams 30 are 
each shown in a dwell position which corresponds to the sign segments 12 
being aligned so that they display an advertising image. Each cam has 
three dwell positions, each dwell position corresponding to one of the 
three display positions of the corresponding sign segments 12. 
The cams 30 are driven by cam drivers assemblies 40 which are each fitted 
to the drive shaft 20 for rotation about the first axis of rotation 22. 
One cam driver assembly 40 drives each of the cams 30. 
Referring now to FIGS. 2-4, details of the drive mechanism are more easily 
seen. As shown in FIG. 4, the cam 30 has an outer perimeter with three 
equally spaced engagement slots 32 extending radially inward from the 
outer perimeter. Positioned between the engagement slots 32 are a total of 
three planar portions which act as stabilizing portions 34. The 
stabilizing portions 34 give the cam 30 a generally triangular shape with 
the engagement slots extending radially inwardly from each of the three 
"points" of the triangle. 
As best shown in FIGS. 2 and 3, the cam driver assembly includes a cam 
driver 42 which extends outwardly from the first axis of rotation 22 and 
terminates in a knob 43. The cam driver 42 is secured to the drive shaft 
20 by a base 44. The knob 43 describes an arc as the cam driver 42 is 
rotated about the first axis of rotation 22. The base 44 has a cylindrical 
bore 46 defined therethrough for accepting the drive shaft 20. Base 44 
also has a slot 48 intersecting the bore 46. A bolt 50 passes through the 
base 44 from one side of the slot 48 to the other so that tightening the 
bolt causes the slot 48 to narrow thereby tightening the bore 46 and 
clamping it securely on the drive shaft 20. By loosening the bolt 50, the 
cam driver assembly 40 can be loosened on the drive shaft 20 and angularly 
repositioned so that the rotational position of the cam driver 42 relative 
to the drive shaft 20 is altered. 
The cam driver assembly 40 also includes a stabilizing member, which in the 
preferred embodiment is a sectioned disk 54 which is bolted to the base 44 
and lies perpendicular to the axis of rotation 22. The sectioned disk 54 
acts as a stabilizing number by contacting one of the stabilizing portions 
34 of a corresponding cam 30 when the cam is in one of its dwell 
positions. This arrangement locks the cam and the corresponding sign 
segment 12 in the proper position when the cam is not being rotated. 
Sectioned disk 54 has a section or relief 56 removed adjacent the cam 
driver 42. The relief 56 has squared off edges 58. The relief 56 allows 
the cam driver 42 to engage the cam 30 without interference. 
Turning now to the operation of the drive mechanism, it can be seen in FIG. 
1 that the leftmost cam 30 is in a dwell position and in this position the 
disk 54 is contacting one of the planar stabilizing portions 34 of the cam 
30. In this position, the drive mechanism locks the cam 30 in the dwell 
position. Turning now to the rightmost cam 30 and cam driver assembly 40 
illustrated in FIG. 1, it can be seen that this cam driver assembly 40 has 
rotated far enough that sectioned disk 54 no longer contacts the planar 
stabilizing portion 34 of the cam 30 and therefore the cam 30 can rotate. 
Referring to FIG. 5, the same situation is shown schematically. In this 
figure, the cam driver assembly 40 has reached a position in which the 
disk 54 is no longer in contact with the stabilizing position 34 of the 
cam 30. At this position, the knob 43 contacts and begins to enter one of 
the engagement slots 32. As the knob 43 engages the engagement slot 32, 
the cam 30 begins to rotate, unhindered by a sectioned disk 54. FIG. 6 
shows the cam at a slightly later point than at FIG. 5. In this figure, 
the cam driver knob 43 is now fully engaged in the engagement slot 32 and 
is rotating the cam 30. Continuing with FIG. 7, the cam 30 is shown 
further rotated with the cam driver knob 43 completely bottomed in the 
slot 32. FIG. 8 shows the same cam 30 now rotated almost completely to its 
next dwell position. In this figure, the knob 43 is almost disengaged from 
the slot 32 and the edge 58 of the recess in the sectioned disk 54 is 
approaching one of the planar stabilizing portions 34 of the cam 30. As 
shown, as the cam driver assembly 40 continues to rotate, the edge 58 of 
the recess in the disk 54 will contact the stabilizing portion 34 of the 
cam 30 thereby pushing the cam 30 completely into a new dwell position. 
Then, as the cam driver assembly 40 continues to rotate, the sectioned 
disk 54 will remain in contact with the stabilizing portion 34 of the cam 
30 thereby holding it in this dwell position until the cam driver once 
again approaches the position shown in FIG. 5. At this time, the cam 30 
will again be rotated to a new dwell position. 
As can be seen, the sectioned disk 54 serves two purposes. First, it acts 
to stabilize the cam 30 in a dwell position when the cam is not being 
rotated by the cam driver knob 43. Secondly, the edge 58 of the recess 56 
in the sectioned disk 54 acts to push the cam 30 the last small amount 
into the new dwell position. 
As will be clear to one of skill in the art and from a study of FIGS. 5-8, 
the combination of the slotted cam 30 and the cam driver assembly 40 cause 
the cam 30 to rotate at a non-uniform speed. As the knob 43 first engages 
the slot 32 in the cam 30, as shown in FIG. 5, the cam 30 rotates very 
slowly. However, as the cam 30 reaches the halfway point to its next dwell 
position, as shown in FIG. 7, the cam 30 will be rotating much faster. 
Then, as the cam 30 approaches its new dwell position, the speed of 
rotation will once again slow as the knob 43 moves down the engagement 
slot and exits as shown in FIG. 8. The cam driver knob 43 moves at a 
constant rotational speed while rotating the cam but the cam rotates 
slowly at first, accelerating to a maximum speed near the center point of 
its rotation, and slowing back down and finally coming to a stop in its 
new dwell position. The variation in rotational speed is due to the 
geometry of the cam 30 and the relative positioning of the cam driver 
assembly 40 and the cam 30. This non-uniform rate of rotation is highly 
desirable for a rotating sign assembly having a plurality of rotatable 
multisided sign segments 12. In a billboard size rotating sign assembly 
10, the individual sign segments 12 are heavy and require a significant 
amount of force to rotate them from one display position to the next. 
Therefore, the stresses in the drive mechanism are reduced by rotating the 
sign segment slowly at first, accelerating, decelerating, and finally 
finishing the rotation slowly. While the stresses could also be reduced by 
performing an entire rotation at a slow speed, this would cause the sign 
segments to remain between display positions for an increased period of 
time which is undesirable for aesthetic reasons. 
Referring to FIG. 2, other aspects of the drive mechanism can be seen. The 
drive shaft 20 is supported by a bearing 16 at one of its ends. As will be 
clear to one of skill in the art, the drive shaft may be supported, and 
driven, in any of a number of ways. The output shaft 24 is supported by a 
bracket and bearing assembly 26. This bearing and support assembly 26 may 
be of many designs as will be clear to those of skill in the art. The 
upper end of the output shaft 24 is a bracket 28 which serves to interface 
with one of the sign segments 12. Depending on the design of the rotating 
sign, the sign segments may have various designs and require various types 
of interfaces. However, the present invention may be made to work with any 
of these rotating sign segments by modifying the bracket 28. 
Referring back to FIG. 1, it can be seen that the three illustrated cam 
driver assemblies 40 are not positioned in the same rotational position 
with respect to the drive shaft 20. This is not only desirable, but is a 
feature of the present invention. As described earlier, the cam driver 
assemblies 40 are adjustably positioned on the drive shaft 20 and can be 
positioned such that their rotational position relative to the drive shaft 
20 is all the same or different from one another. It has been found that 
sequentially rotating the various sign segments 12 can give a highly 
pleasing effect. For example, rotation of the sign segments 12 near the 
center of a billboard rotate slightly before their neighboring sign 
segments, causes the change from one advertising message to the next to 
appear to sweep from the center of the rotating sign 10 to the sides much 
like the opening of a curtain. This is accomplished by rotationally 
positioning the cam driver assemblies 40 such that the cam driver 
assemblies near the center of the rotating sign 10 engage their 
corresponding cams 30 prior to the cam driver assemblies further from the 
center of the sign. Each cam driver is offset slightly from the cam driver 
next to it so that rotation of the sign segments 12 flow smoothly from the 
center to the sides of the sign 10. An alternative effect can be achieved 
by positioning the cam driver assemblies such that a change from one 
advertising display to the next appears to sweep from one side of the sign 
to the other. The appearance of the change sweeping from a portion of the 
sign to the other is especially desirable where all three of the 
advertising displays are somehow related. In this way, the displays can be 
made to flow into one another enhancing their effect. While the sequential 
rotation effect is highly desirable for some applications, other 
applications may not benefit from the effect or the effect may be 
distracting or otherwise undesired by the advertiser. Therefore, it is 
highly desirable that the rotational positions of the cam driver 
assemblies 40 be adjustable so that the same rotating sign 10 can be 
changed from a standard setup where all segments rotate at the same time 
to a set up which gives a sweeping affect. Prior approaches to providing 
sequential rotation of sign segments did not allow for adjustment. 
However, the present invention can be easily adjusted after or when the 
sign is installed. 
The drive shaft 20 may be rotated at a constant speed without stop or it 
may be started and stopped as necessary. If the drive shaft 20 is rotated 
at a constant speed, the amount of time one message is displayed and the 
speed at which the segments 12 are rotated will be directly related to 
each other. Unlike with prior art signs, where stopping the sign segments 
12 at a display position meant stopping the drive shaft 20 in a specific 
position, the present invention allows the drive shaft 20 to be rotated at 
a constant rpm therefore avoiding complications associated with starting 
and stopping the drive motor. However, if it is desired that the time 
which each display is left in the display position be increased, the drive 
shaft 20 can be stopped following each rotation allowing the advertising 
display to remain visible for a longer period of time. The drive shaft 20 
may also be reversed between clockwise and counterclockwise rotation if 
desired. This may be useful where only two advertising displays on a three 
sided signs are to be displayed such as when one of the advertisers has 
not yet paid for their side of the sign. Unlike prior art designs where 
the drive shaft must be stopped in a precise position to allow display of 
one of the advertising displays, in the present invention, the drive shaft 
20 can be stopped in a variety of positions so long as the cam driver 
assemblies 40 do not have their knobs 43 engaging the cams 30. This leaves 
a wide range in which the drive shaft 20 may be stopped which reduces the 
cost and complexity of the control devices necessary for a drive motor. 
In view of the teaching presented herein, other modifications and 
variations of the present invention will be readily apparent to those of 
skill in the art. The foregoing drawings, discussion, and description are 
illustrated of some embodiments of the present invention but are not meant 
to be limitations on the practice thereof and it is the following claims, 
including all equivalents which define the scope of the invention.