Rotating paddle bin level indicator

Apparatus for indicating the level of flowable material in a storage bin comprising a motor rotatably suspended by a spring within a protective enclosure and a drive shaft coupled by a ball-and-detent clutch to a paddle disposed within the bin to engage material therein. When the material reaches the level of the paddle, the drag on the paddle causes the motor to rotate within the enclosure and thereby to activate a switch disposed within the enclosure and coupled to the motor. A spring returns the motor to the switch-deactivated position when the material level decreases and the consequent drag is removed from the paddle. Electronic circuitry disposed within the housing includes field-selectable fail-safe circuitry for indicating either a high or a low material condition in the event of a power failure or the like independently of actual material level.

The present invention relates to bin level indicators, and more 
particularly to an improved apparatus of the rotating paddle type for 
indicating the level of flowable material in a storage tank or bin. 
Bin level indicators of the above-noted type typically comprise a motor 
carried for limited rotation within a protective enclosure and connected 
to a rotatable paddle which is adapted to engage flowable material within 
a storage bin when the material rises to the bin level at which the 
rotating paddle is disposed. The material drag on the paddle causes the 
motor drive torque to rotate the motor rather than the paddle, which 
rotation is normally sensed by one or more switches carried within the 
enclosure. The switches may be connected to deactivate a conveyor feeding 
material to the bin, to remove power from the indicator motor and/or to 
perform other control functions related to material level. Two examples of 
bin level indicators of the described type are shown in the U.S. patents 
of Grostick Nos. 2,851,553 and Gruber 3,542,982. 
It is an object of the present invention to provide an improved rotating 
paddle bin level indicator which is more economical to fabricate and 
assemble than are prior art indicators of similar type. In furtherance of 
the object stated immediately above, it is another object of the invention 
to provide an improved rotating paddle bin level indicator which has a 
reduced number of component parts, and in which component parts may be 
either purchased as standard off-the-shelf elements or may be fabricated 
at minimum expense. 
Another important and yet more specific object of the present invention is 
to provide a rotating paddle bin level indicator which includes a 
so-called "fail safe" feature for automatically indicating a predetermined 
material level--i.e., either high or low material level--independently of 
actual material level in the event of a power or motor failure. A further 
and related object of the invention is to provide such fail safe feature 
which is selectable in the field for indicating either a high level or a 
low level material condition in the event of failure as described.

Referring to FIGS. 1-4, a presently preferred embodiment 10 of the bin 
level indicator provided by the present invention includes a generally 
rectangular protective housing or enclosure 12 comprising a shallow 
cup-shaped enclosure base 14 and a deeper cup-shaped enclosure top or 
cover 16. Cover 16 is mounted to base 14 by bolts 18 extending through 
apertures in a radially extending flange 20 on cover 16 into threaded 
apertures in a corresponding base flange 22. A sealing gasket 24 is 
disposed between the respective flanges. A hollow externally threaded 
nipple 26 extends outwardly from base 14 and is adapted to be threadably 
received in a corresponding internally threaded gland 28 (FIG. 1) carried 
by the wall of a material storage tank or bin 30. An internally threaded 
laterally opening hole 32 (FIG. 1) is formed adjacent base flange 22 to 
receive a strain relief grommet or the like through which is fed a 
multiple-conductor electrical cable 36 adapted for connection to level 
indicating apparatus (not shown) disposed externally of enclosure 12. 
Internally, indicator 10 includes an open generally C-shaped bracket 38 
having lower flanges 40 mounted by screws 42 to base 14. An electronics 
assembly 44 is carried above the upper bridging portion 46 of bracket 38 
by the spacers 48 received by snap fit into corresponding openings on 
bracket 38. Electronics assembly 44 includes a pair of terminal blocks 
51,52 mounted on an upper surface of a planer circuit board 50 and a relay 
assembly 53 suspended beneath circuit board 50. Electronics assembly 44, 
including relay assembly 53, will be described in greater detail 
hereinafter in connection with FIG. 5. 
A motor 54 is carried within enclosure 12 and comprises a generally 
cylindrical motor housing 56 having a rotatable shaft 58 (FIG. 3) 
extending axially from one end thereof eccentrically of housing 56. A 
coiled spring 60 is disposed between motor housing 56 and bracket bridge 
portion 46 positioned thereabove. Spring 60 is held in axial alignment 
with shaft 58 by a boss or eye 62 extending downwardly from bracket 
portion 48 into the spring coils and by an opposing boss 64 extending 
upwardly from the motor housing. The motor 54 shown in the drawings is 
purchased from Hansen Manufacturing Company, of Princeton, Ind. under part 
No. 34668RK247RL and includes a number of apertured ears extending 
radially outwardly from a portion of the housing 56 adjacent shaft 58. A 
coil spring 74 (FIG. 4) extends between an aperture 76 in bracket 38 and a 
housing ear 68 to bias motor housing to a normal or rest position shown in 
the drawings. 
A switch 78 is mounted by an L-shaped bracket 82 (FIG. 3) to motor housing 
56 and has a switch actuator button 80 extending laterally toward an 
opposing edge or surface of bracket 38. In the normal or rest position of 
motor 54, actuator button 80 is spaced from the opposing bracket 38, as 
best seen in FIG. 3. However, when motor shaft 58 is held against rotation 
by material engaging paddle 118 (FIG. 1), motor housing 56 rotates against 
the force of spring 74 until button 80 abuts bracket 30 to actuate switch 
78. Spring 74 will return motor housing 56 to the normal or rest position 
upon removal of material drag from the motor shaft as hereinabove 
described, thereby causing deactivation of switch 78. 
Drive shaft 58 has a forked end received in the collar element 98 of a 
ball-and-detent clutch assembly 100 (FIG. 3) and is rotatably coupled 
thereto by means of a pin 102 extending across collar 98. A paddle drive 
shaft 104 terminates internally of enclosure 12 in a hub 106 having a 
cylindrical bore 108 extending diametrically therethrough. A coil spring 
110 and a pair of balls 112 are disposed in hub hole 108 with the balls 
112 protruding radially from opposite ends of the hole in the rest 
condition of spring 110. Clutch collar 98 has an axially extending flange 
114 which surrounds hub 106. A pair of holes 116 are formed radially in 
the flange opposite remote ends of holes 108 to receive the protruding 
portions of the respective balls 112. As clutch collar 98 is axially 
assembled over drive shaft hub 106, spring 110 and balls 112 are forced 
radially inwardly such that the spring is in compression and holds the 
balls in yieldable engagement with the corresponding flange holes 116. 
During normal operation, balls 112 remain engaged with the corresponding 
holes 116 in clutch collar 98 and the rotary motion of motor shaft 58 is 
transmitted through the clutch assembly 100 to drive shaft 104. Should 
rotation of drive shaft 104 be impeded by impact of material in contact 
with paddle 118 (FIG. 1) directly coupled thereto, the tendency of motor 
shaft 58 and clutch collar 98 to continue rotating relative to shaft hub 
106 forces balls 112 to roll over the edges of holes 116 in clutch collar 
flange 114 so as to be driven radially inwardly against the force of 
spring 110 to a retracted position in hub bore 108. Thus, excessive torque 
on motor shaft 58 causes the balls and the flange holes to become 
disengaged, whereby motor shaft 58 is free to rotate. Clutch 100 thereby 
disengages the paddle and drive shaft from the motor in the event of shock 
loading of the paddle by impact of material thereon. This safety 
arrangement prevents damage to the motor internal gear train. After 
180.degree. of motor shaft rotation, the balls 112 again register with the 
apertures 116 in clutch collar 98. The balls will again disengage from the 
clutch collar if rotation of drive shaft 104 is still impeded, such 
repetitive engagement and disengagement continuing until the resistance to 
rotation of the drive shaft and the clutch collar drops below a value 
corresponding to the torque transmission limit of clutch assembly 100. 
Drive shaft 104 extends through the roller bearings 120,122 which are 
press-fitted into corresponding recesses in enclosure mounting nipple 26, 
and is axially positioned therein by the retaining rings 124,126 received 
in corresponding grooves in the drive shaft on respectively opposite sides 
of bearings 120,122. An annular leaf spring or belleville washer 128 is 
captured between retaining ring 126 and bearing 122 to absorb axial shock 
on the drive shaft caused by rocks or the like striking paddle 118. Thus, 
drive shaft 104 is held in fixed axial position with respect to apparatus 
enclosure 12, and motor 54 effectively floats within the enclosure. More 
specifically, motor housing 56 is biased by spring 60 into face-to-face 
axial engagement with clutch collar 98 with a thrust washer bearing 130 
being disposed therebetween. Thus, motor 54 is effectively vibrationally 
isolated from housing 12 and is free to float relative thereto by the 
relatively loose fit of shaft forked end 98 over pin 102 and by the 
shock-absorbing spring 60. 
A sealing assembly 142 is press-fitted into the housing-remote end of gland 
26 and comprises a collar 144 having a radially inwardly directed channel 
which receives a resilient lip-sealing element 146 and an annular spacer 
element 148 which firmly pinches an end of sealing element 146 within the 
collar. Paddle 118 shown in FIG. 1 terminates in a collar 120 (FIG. 2) 
which is rotatably coupled by a pin 122 to an end of drive shaft 104 
received telescopically therein. Paddle 118 per se is the subject of the 
U.S. patent to Fleckenstein No. 4,095,064 assigned to the assignee hereof. 
Bin level indicator 10, to the extent thus far described, with the 
exception of electronics assembly 44 to be described in detail 
hereinafter, is similar in many important respects to that which is the 
subject of the U.S. patent to Levine No. 4,147,906 which is also assigned 
to the assignee hereof. The disclosures of both said patents to 
Fleckenstein and Levine are incorporated herein by reference. 
FIG. 5 is a schematic diagram of electronics assembly 44 shown in FIGS. 
2-4. It will be understood and appreciated that the various conductors 
shown schematically in FIG. 5, which are generally in the form of 
conductive foils etched onto board 50 and suitable lead wires extending to 
motor 56 and switch 78, have been omitted from FIGS. 2-4 for purposes of 
clarity. 120 VAC input power for operation of indicator 10 and the various 
control output signals are fed to and from indicator 10 by cable 36 (FIG. 
1). It will be understood that the various conductors of cable 36 are 
connected within indicator 10 to corresponding terminals on blocks 51,52, 
although such connections have been omitted from FIGS. 2-5 for purposes of 
clarity. 
The "hot" side of 120 VAC input power received at terminal block 51 via 
cable 56 (FIG. 1) is connected through a fuse 200 and corresponding 
terminals of the mated connectors indicated generally at 202 to motor 54. 
Input power is also fed through connectors 202 to the common terminal of 
switch 78 (FIGS. 3 and 5). The normally closed and normally open terminals 
of switch 78 are respectively connected through connectors 202 and then 
through corresponding jumpers 204,206 (FIGS. 2 and 5) to one side of the 
actuating coil 208 of relay assembly 53. Both jumpers 204,206 are 
installed at the factory, one or the other of such jumpers being intended 
for removal upon installation of the bin level indicator for selecting 
either low level fail safe operation (removal of jumper 204) or high level 
fail safe operation (removal of jumper 206) in the manner to be described. 
The double pole contacts 210 of relay assembly 53 are connected to 
terminal block 52, and thence via cable 36 (FIG. 1) to remote indicating 
and/or control means (not shown). 
The "neutral" side of 120 VAC input power is connected from terminal block 
51 through a resistor 212 and connectors 202 to motor 54. The control or 
gate electrode of a triac 214 is connected to the juncture of resistor 212 
and connectors 202 through a resistor 216. The primary current conducting 
electrodes of triac 214 are respectively connected to the neutral side of 
input power and the second side of relay actuating coil 208. The juncture 
of triac 214 and relay coil 208 is also connected to a terminal of block 
51 for indicating a motor power failure via cable 36 (FIG. 1) as will be 
described. Switch 78 and relay switches 210 are illustrated in FIG. 5 in 
their respective normal positions when rotation of paddle 118 is unimpeded 
and motor 54 is in the position illustrated in FIG. 3. The purpose of 
connectors 202 is to permit rapid replacement of electronics assembly 44 
without removing motor 54 and switch 78. 
As previously indicated, jumpers 204 and 206 are for respectively selecting 
either high or low level fail safe operation in accordance with the 
present invention. The terms "high level fail safe" and "low level fail 
safe" have their usual meaning in the art and refer simply to the material 
level indication desired by an operator in the event of a power failure or 
the like. For example, if an operator is to position indicator 10 in the 
upper position of a bin to indicate a bin-full condition and would like 
the indicator to indicate a bin-full condition in the event of power or 
motor failure so that the bin would not overfill, he would select the high 
level fail safe mode of operation by removing jumper 206 prior to 
installation. It will be appreciated, of course, that "high" and "low" are 
taken with respect to indicator position in a tank, "high" being a 
material position at which rotation of paddle 118 is obstructed by 
material, and "low" being material positions at which paddle rotation is 
unobstructed. 
In operation with 120 VAC power applied to terminal block 51, triac 214 is 
normally turned on through resistors 212,216 and motor 54 is normally 
energized through fuse 200. Assuming that high level fail safe operation 
has been selected as previously described, whereby jumper 206 has been 
removed while jumper 204 remains in place, the coil 208 of relay assembly 
53 is normally energized through switch 78, jumper 204 and triac 214. When 
the material in the bin rises to the level of indicator 10 and rotation of 
paddle 118 is retarded, switch 78 is actuated as previously described, and 
relay assembly 53 is de-energized to provide an indication of a high 
material level via relay contacts 210, terminal block 52 and cable 36 
(FIG. 1). If the material level subsequently falls below the level of the 
indicator and paddle 118 resumes rotation, switch 78 will return to the 
normal condition (FIG. 5) and relay 53 will be re-energized. 
In the event of a power failure, again assuming selection of high level 
fail safe operation as described, relay coil 208 will be de-energized, 
indicating in effect a high material level independently of actual 
material level. Similarly, in the event that motor 54 or fuse 200 burns 
out, control power is removed from the gate of triac 214, the triac opens, 
operating in effect as an electronic switch, and coil 208 of relay 53 is 
de-energized to indicate a high material level condition independently of 
actual material level. 
Assuming now that low level fail safe operation has been selected by 
removing jumper 204 and leaving jumper 206 in place, when material is 
above the level of the indicator and rotation of the paddle is retarded, 
relay 53 is energized through switch 78 (which is actuated to the normally 
open condition in FIG. 5 when paddle rotation is retarded) and jumper 206. 
When the material level falls below the indicator position and the paddle 
begins rotation, switch 78 assumes the position shown in FIG. 5 and relay 
53 is de-energized. Likewise, relay 53 is de-energized by triac 214 in the 
event of a power, fuse or motor failure to indicate a low level condition 
independently of actual material level. 
Thus, it will be appreciated in accordance with the invention that triac 
214 cooperates with jumpers 204,206 and switch 78 to maintain relay 53 
normally energized in the absence of the condition to be indicated, either 
high or low material level, and to de-energize relay 53 either upon actual 
occurrence of the material level of interest or upon occurrence of a 
failure condition. 
Connection of the control electrode of triac 214 in the current path of 
motor 54 results in de-energization of relay 53 in the absence of motor 
current independently of the condition of switch 78 and independently of 
jumpers 204,206. Likewise, jumpers 204,206 cooperate with switch 78 
normally to energize relay 53 in the absence of the material level of 
interest, so that a power failure, as well as a change in material level 
(or a motor or fuse failure) will be reflected by a de-energized relay. 
The state of triac 214 provides an indication of proper motor operation 
independently of material level--i.e. triac 214 is in a conductive 
condition as long as power is applied and motor 54 is conducting current. 
Thus, the conductive condition of triac 214 may be remotely monitored by 
connecting a lamp 222, for example, between the hot side of input power 
and a cable conductor connected through terminal block 51 to the juncture 
of triac 214 and relay coil 208. When triac 214 is conducting, the hot and 
neutral sides of AC power will appear across the lamp and the lamp will be 
lit. In the event of motor or fuse failure, triac 214 becomes 
non-conducting and the lamp will be extinguished. 
Although the invention has been described in detail in connection with a 
preferred embodiment thereof, any number of modifications may be 
effectuated without departing from the scope of the invention in its 
broadest aspects. For example, triac 214 could be replaced by another type 
of electronic switch, such as an electromagnetic relay having an actuator 
coil connected in series with motor 54 and a pair of normally open 
contacts connected in series with relay coil 208. Similarly, relay 53 
could be replaced by solid state switches or the like, although 
electromagnetic relays are preferred in the art in this application by 
reason of the effective isolation of the relay contacts 210 from the 
remainder of the circuitry. Jumpers 204,206 could be replaced by a 
suitable single pole double pole switch located either within or remotely 
of indicator 10. However, it has been found as a practical matter that 
there is little, if any, demand in the art for provision of a feature 
whereby a particular unit may be switched between high and low level fail 
safe during the lifetime of the unit. 
It will also be apparent that the fail safe feature of the invention is not 
limited to the particular presently preferred embodiment of indicator 
shown in the drawings, and may as readily be incorporated in the 
indicators disclosed in the above-referenced Fleckenstein and Levine 
patents, for example, where the switches for detecting limited 
counter-rotation of the paddle drive motor are fixedly carried in the 
indicator housing. Likewise, the invention is not limited to rotating 
paddle units wherein limiting of paddle rotation results in limited rotary 
motion of the drive motor. Other mechanical motion or counter motion could 
as well be utilized to actuate switch 78. 
Thus, in accordance with a first important aspect for maintaining the level 
indicating first relay means 53 normally energized so long as power is 
applied to the unit and the material has not reached or assumed the 
preselected actual condition of interest, i.e., either high or low level, 
the present invention contemplates operator-selectable switch means, 
specifically jumpers 204,206, in combination with double pole sensing 
switch for normally establishing a current path through the first relay 
means. In accordance with a second important aspect, a second relay means, 
i.e., triac 214, is responsive to continued current flow through motor 54, 
indicative of continued application of power through fuse 200 and 
continuity through the motor windings, for maintaining the current path 
through the level indicating first relay means. Thus, these first and 
second aspects of the invention combine to provide a rotating paddle bin 
level which includes an operator selectable fail safe feature for 
indicating either a high level or low level material condition in the 
event of power or motor failure and independently of the actual material 
level.