Information
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Patent Grant
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6360463
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Patent Number
6,360,463
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Date Filed
Thursday, October 29, 199825 years ago
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Date Issued
Tuesday, March 26, 200222 years ago
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Inventors
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Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
A convertible sign mechanism is provided which comprises a convertible sign member that is rotatable about an axis. The convertible sign member is capable of rotating at a variable velocity. A motor is operatively connected to a drive shaft, which is connected to a cam follower. The cam follower is slidably connected to a member receiving the cam follower, with the receiving member being connected to an output gear. The output gear is connected to a drive gear, which together provide a reduction ratio of at least 2:1.
Description
FIELD OF THE INVENTION
The present invention relates to a variable speed rotary drive mechanism. More specifically, the present invention includes a drive mechanism useful in operating display sign elements, such as those on prismatic displays, so as to vary the speed of rotation from a maximum velocity occurring during the changing of display surfaces to a minimum velocity occurring as the position corresponding to the display of the desired surface is approached.
BACKGROUND OF THE INVENTION
There are several known kinds of convertible signs, one type of which creates a display arrangement comprising single or multiple prisms, each of which are mounted at opposite longitudinal ends and rotatable about their longitudinal axis. in the case of multiple prisms, each prism is part of an equal sequence in a frame, the prisms residing beside each other. The sides of the prism are oriented in a permanently occurring sequence forming a number of displays corresponding to the number of side surfaces of the single prism. Such a sign necessarily includes a drive motor for synchronous rotation of the prisms via a transmission.
Displays of this type usually comprise triangular aluminum prisms, which rotate in an aluminum frame and show three displays in permanently recurring sequence. The prisms can be dismounted and exchanged. Due to the triangular shape of the prisms, three different views can be shown. The display arrangement can be mounted with its frame standing free, on walls or on roofs of buildings. Also, single prism signs are typically found on scoreboards in arenas or the like.
Known display arrangements of this type are typically driven by an electric motor, and the prisms are rotated synchronously by a gear transmission in such a manner that the sides of the respective prisms belonging to the same picture are shown simultaneously and form a display. The gear transmission ensures synchronous rotation of each prism.
A gear transmission, however, involves certain disadvantages. A desirable characteristic of most convertible signs is that they operate noiselessly, particularly when the displays are mounted on buildings. A gear transmission for operating noiselessly requires good lubrication. This requirement would be difficult to attend to at many sign locations, because of the need for periodic service and such signs in most cases are positioned in places of difficult access. The problem of access has created a need for mechanisms of high durability and reliability, along with the continuing requirement for accurate registration of the sign elements and the constant need to start, rotate and stop the sign display. Experience in the field has demonstrated the need to convert this inherently complex mechanical operation into one having as much reliability and simplicity as possible.
A recent solution to these problems is disclosed in commonly assigned U.S. Pat. No. 5,343,645, issued to Huber. There is disclosed a chain driven gear drive system, including off-center gear elements. These gear elements are rotated to translate various potential speeds to a mounting gear, on which a sign member is mounted. As a result of this structure, the sign member rotates through successive 120° turns while varying the speed of rotation from a maximum velocity occurring during the changing of display surfaces to a minimum velocity occurring as the position corresponding to the new display surface of the sign member, of the sign is approached.
What is needed is an alternate drive mechanism for driving display sign arrangements and other devices that require frequent start and stops.
SUMMARY OF THE INVENTION
The present invention provides an alternate variable speed rotary drive mechanism for operating display sign elements, such as those on prismatic displays, so as to vary the speed of rotation from a maximum velocity occurring during the changing of display surfaces to a minimum velocity occurring as the position corresponding to the display of the desired surface is approached. The variable speed rotary drive mechanism can also be used to drive other devices requiring frequent starts and stops, such as conveyors.
In one embodiment in accordance with the invention, a convertible sign mechanism is provided which comprises a convertible sign member that is rotatable about an axis. A drive means is connected to the convertible sign member for rotating the convertible sign member at a variable velocity, with the drive means operating continuously throughout the rotation of the convertible sign member. The drive means includes a motor, a drive shaft operatively connected to the motor, a cam follower operatively connected to the drive shaft, a member configured to receive the cam follower in a slidable engagement, an output gear operatively connected to the member; and a drive gear operatively connected to the output gear and to the convertible sign member. The output gear and the drive gear provide a reduction ratio of at least 2:1.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying description, in which there is described a preferred embodiment of the invention.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1
is a perspective view of the convertible sign mechanism in accordance with the invention;
FIG. 2
is a side view of the of the mechanism, with the motion transmission device in a first position;
FIG. 3
is a schematic view of the motion transmitting device in a first position;
FIG. 4
is a schematic view of the motion transmitting device in a second position;
FIG. 5
is a schematic view of the motion transmitting device in a third position; and
FIG. 6
is a schematic view of the motion transmitting device in a fourth position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIG. 1
, a convertible sign mechanism according to the principles of the invention is shown generally at
10
. The convertible sign mechanism
10
includes a multifaceted prismatic display member
12
, which can have two or three sides, but in the specific example is shown to have three-sides
14
,
16
,
18
. The sides
14
,
16
,
18
typically contain different information, and when in a multiple prismatic sign, are typically ganged or combined together with similar display members in a coordinated manner to form the desired sign. The mechanism
10
further includes a drive mechanism
20
for rotating the display member
12
about its central axis so that each side
14
,
16
,
18
is periodically brought into view.
With reference now to
FIGS. 1 and 2
, the drive mechanism
20
generally includes a suitable electric motor
22
having a drive shaft
24
with a pinion gear
26
fixed thereto, such that the pinion gear
26
is rotatably driven by the motor
22
. The motor
22
is typically timed by conventional timing devices or the motor can be under computer control. An endless chain
28
is disposed over the drive gear
26
and an input gear
30
that is fixed to an input shaft
32
which forms the input to a variable speed, motion transmitting device
34
. An output shaft
36
extends from the device
34
and has an output gear
38
fixed thereon so as to rotate with the output shaft
36
. A second endless chain
40
is disposed over the output gear
38
and a large diameter drive gear
42
that is fixed to a shaft
44
which is connected to the display member
12
.
When the motor
22
is activated, the drive shaft
24
rotates the pinion gear
24
which drives the endless chain
28
. The endless chain
28
in turn drives the input gear
30
, thereby rotating the input shaft
32
. The motion transmitting device
34
continuously varies the rotational speed input by the input shaft
32
, so that the rotational speed of the output shaft
36
and the output gear
38
are continuously varied. The rotation of the output gear
38
is transmitted by the endless chain
40
to the large diameter drive gear
42
which drives the shaft
44
thereby causing the display member
12
to rotate so as to change the side
14
,
16
,
18
that is viewed.
A concern when driving members that are periodically stopped and started, such as prismatic display members and conveyor systems which stop and start at fill stations, is that the initial start of movement from a fully stopped condition be gradual. The movement speed should eventually build up to a maximum, and then gradually decrease as the driven member starts approaching its next intended position. Applicant's have found that this gradual increase and gradual decrease of movement speed avoids the shock of abrupt starts and stops, and minimizes wear on components.
In order to accomplish the gradual increase and gradual decrease of the rotational speed of the display member
12
, the motion transmitting device
34
is specifically designed to convert the constant speed rotational input provided by the input shaft
32
into a smooth, cyclically varying speed, accelerating-decelerating rotational output to the output shaft
36
.
With reference specifically to
FIG. 2
, it is seen that the motion transmitting device
34
includes a pair of spaced side walls
46
,
48
, each of which includes a bearing
50
,
52
associated therewith for rotatably supporting the respective shafts
32
,
36
. A cam follower arm
54
is suitably fixed to the end of the input shaft
32
, such as by a key, so as to rotate with the input shaft
32
. A follower
56
, such as a rotating bearing or a sliding bearing, is fixed to the follower arm
54
and is spaced radially of the axis of the input shaft
32
. A cam arm
58
is suitably fixed at one end thereof to the end of the output shaft
36
, such as by a key, whereby the cam arm
58
is eccentrically mounted. The cam arm
58
includes a slot
60
formed therein which extends longitudinally the length of the cam arm
58
, and the follower
56
is slideably received within the slot
60
. Thus, as the input shaft
32
rotates, the output shaft
36
rotates as a cyclically varying speed due to the cam and follower arrangement.
Preferably, the follower
56
is spaced from the axis of the input shaft
32
a distance slightly greater than the distance between the axes of the input and output shafts. Thus, as the input shaft
32
rotates, the cam follower arm
54
and the follower
56
rotate therewith. Rotation of the follower arm
54
and follower
56
causes the cam arm
58
and the output shaft
36
to rotate. The rotational speed of the input shaft
32
can be assumed to be constant, and therefore due to the arrangement of the device
34
, the rotational speed of the output shaft
36
will vary from a maximum when the follower arm/follower
54
,
56
and the cam arm
58
are in the position shown in
FIGS. 2 and 3
, to a minimum when the follower arm/follower and cam arm are displaced 180° to the position shown in FIG.
5
. The transition between maximum and minimum rotational speeds of the output shaft
36
occurs in an extremely smooth manner due to this arrangement, such that abrupt starts and stops are avoided.
The variation in rotational speed occurs based upon the distance of the follower
56
from the axis of the output shaft
36
. Referring now to
FIGS. 3-6
, when the follower
56
is at its maximum distance from the output shaft axis, as illustrated in
FIG. 3
, the torque acting on the cam arm
58
is greatest since the moment arm D of the force acting on the cam arm is at its maximum. As the elements rotate to the position shown in
FIG. 4
, the follower
56
is moving toward the output shaft
36
, and thus the rotational speed of the output shaft
36
is continuously decreasing. When the elements reach the position shown in
FIG. 5
, the follower
56
has moved to its closest distance to the output shaft axis. Therefore, the torque acting on the cam arm
58
is at its minimum, since the moment arm of the force is at its minimum. As the elements rotate from the position shown in
FIG. 5
to the position shown in
FIG. 6
, the follower
56
moves away from the output shaft
36
so that the rotational speed thereof gradually increases.
It is important that the follower
56
be spaced from the axis of the input shaft
32
a distance slightly greater than the distance between the axes of the input and output shafts, i.e. the axis of the follower
56
, should not coincide with the axis of the output shaft
36
. This prevents binding of the follower
56
in the cam arm
58
, which would stop rotation of the output shaft
36
and possibly damage the components.
Assuming that the display member
12
is initially at rest and the side
14
is currently viewable, then to view the side
16
the display member
12
must be rotated about its axis. This is accomplished by activating the motor
22
, which drives the input shaft
32
in the suitable direction. Initially, the follower
56
and cam arm
58
are in their minimum rotational speed position (FIG.
5
). When the input shaft
32
is rotated, the follower arm
54
/follower
56
start driving the cam arm
58
, with the rotational speed gradually increasing as the follower
56
and cam arm
58
move away from the minimum speed position (FIG.
6
). Concurrently, the display member
12
starts to gradually rotate from its stopped position.
Continued rotation causes the follower
56
and cam arm
58
to reach their maximum speed position (FIG.
3
), at which point the display member
12
is being driven at its maximum speed and the side
16
is partially visible. As the follower
56
and cam arm
58
move from the maximum speed position, the speed of the display member
12
starts decreasing as the side
16
of the display member is starting to approach its fully viewed position (FIG.
4
). When the side
16
reaches its fully viewed position, the follower
56
and cam arm
58
will be back at their minimum speed position (FIG.
6
). To stop the display member
12
in position, one need only to deactivate the motor
22
at the minimum speed position.
Ideally, for a three-sided (prismatic) display member
12
, the output gear
38
and the large diameter drive gear
42
are sized to provide a 3:1 reduction ratio, such that a complete cyclic speed variation provided by the motion transmitting device
34
occurs for every 120° rotation of the display member
12
. This ensures that the display member
12
goes through the cycle of gradual speed increase, maximum speed, and gradual speed decrease to minimum speed each time a new side is to be viewed. For a two sided display member a 2:1 reduction ratio would be provided.
While the invention has been described herein as driving a display member, the invention could also be used to drive any member requiring frequent starts and stops, such as conveyors with containers thereon which stop and start at fill stations to fill the containers. The gradual increase and decrease of speed provided by the motion transmitting device described herein would prevent the containers on the conveyor from tipping over, with the maximum speed between starting and stopping maintaining efficient operation of the conveyor.
The above specification provides a complete description of the manufacture and use of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.
Claims
- 1. A convertible sign mechanism comprising:a convertible sign member being rotatable about an axis; drive means connected to said convertible sign member for rotating said convertible sign member at a variable velocity, said drive means operating continuously throughout the rotation of said convertible sign member, said drive means including: a motor; a drive shaft operatively connected to said motor; a cam follower operatively connected to said drive shaft; a member configured to receive said cam follower in a slidable engagement; an output gear operatively connected to said member; and a drive gear operatively connected with said output gear and said convertible sign member; said output gear and said drive gear providing a reduction ratio of at least 2:1.
- 2. The convertible sign mechanism of claim 1, wherein said reduction ratio is 3:1.
- 3. The convertible sign mechanism of claim 2, further comprising a prismatic display arrangement.
- 4. The convertible sign mechanism of claim 1, member configured to receive said cam follower includes a slotted cam arm.
- 5. A convertible sign mechanism having drive means for rotating a structure in a continuous manner at a variable velocity, said drive means comprising:a motor; a drive shaft operatively connected to said motor; a cam follower operatively connected to said drive shaft; a member configured to receive said cam follower in a slidable engagement; an output gear operatively connected to said member; a drive gear operatively connected to said output gear and effective for being operatively connected to a structure to be rotated: and said output gear and said drive gear providing a reduction ratio of at least 2:1.
- 6. The convertible sign mechanism of claim 5, wherein said reduction ratio is 3:1.
- 7. The convertible sign mechanism of claim 5, wherein said member configured to receive said cam follower includes a slotted cam arm.
US Referenced Citations (14)