Rotary Limit Switch

Every motorized Worm Gear Screw Jack must be controlled so that power to the motor is turned off and the brake engaged before the limits of mechanical travel are reached. The ActionJac™ rotary limit switch senses extension shaft rotation and provides switch contact closures that can be used to control motors.

This sturdy, durable assembly is available with two or four circuits or two circuits and a potentiometer. Each circuit has a separate rotating cam that actuates a high quality switch. The switch actuation may be individually and infinitely adjusted anywhere within the travel of the jack.

These assemblies contain gear reducers with ratios that vary according to the model and travel of the jack. Nook selects ratios that result in maximum cam rotation for best accuracy, repeatability and minimum hysteresis. In most cases, with full travel of the actuator, the cam will rotate 3/8 to 7/8 of a revolution to actuate a switch. In the event that the cam continues to rotate, the switch returns to its original state after approximately 25° of rotation, with no damage to the limit switch assembly.

The 2-circuit switch assembly is useful for limiting the maximum and minimum extension. The 4-circuit assembly gives the possibility of additional signals for other user purposes. The potentiometer version is used to provide an analog signal for sensing jack position. Single Pole Double Throw (SPDT) switches are standard and Double Pole Double Throw (DPDT) switches are optional. These assemblies are dust protected and meet NEMA 4 and 5 standards for oil and water tightness.

The ActionJac™ rotary limit switch assembly is mounted to the extension shaft side of the ActionJac™ Worm Gear Screw Jack opposite the input.

The rotary limit switch is available for ActionJac™ Worm Gear Screw Jack sizes 2 tons and larger. Most jack models have close and extended mounts to provide clearance around the switch housing. See the following chart for dimensions.

Switches are factory installed to assure proper assembly in the correct orientation for the specified mounting position.

How To Order a Rotary Limit Switch

Insert the correct designation in the ActionJac™ Worm Gear Screw Jack reference number (see page 31 and 69 of our Worm Gear Screw Jacks Catalog for more information on jack reference numbers).


Please (See Image 3 in Figure 1 Below) for Rotary Limit Switch Positions

Examples of Rotary Limit Switch Designations:

2CA-4C - Rotary Limit Switch, 2-circuit, SPDT, position 4, close mount
4CE-1E - Rotary Limit Switch, 4-circuit, DPDT, position 1, extended mount
C = Close mount on
E = Extended mount (Please see Images below)
Product Code Number of Circuits Switch Type Potentiometer

Dimensions (in)
Circuits A B C D E F
LS-2C 2 CIRCUIT 2.46 5.25 6.24 7.62 34-NPT 3.25
LS-4C 4 CIRCUIT 2.46 5.25 8.24 9.62 1-NPT 3.88
LS-2PT 2 CIRCUIT W/POTENTIOMETER 2.46 5.25 8.24 9.62 1-NPT 3.88

Model Dim. H Close Mount (in) Dim. H Ext. Mount (in) Close Mount Positions
2-BSJ & MSJ N/A 3.56 All
2R, 2.5-BSJ & MSJ 2.75 3.56 All
3-BSJ N/A 3.56 All
5-BSJ & MSJ 3.56 4.56 All
10, 15-BSJ & MSJ 3.88 5.56 All
20-BSJ & MSJ 4.41 5.81 All
30, 35-MSJ 5.25 7.06 All
50-BSJ & MSJ 6.25 11.06 1, 2, 4, 7
75-BSJ & MSJ 7.25 12.06 All
100-BSJ & MSJ 8.25 12 1, 2, 4, 7

IMPORTANT: These designation numbers are not complete part numbers. These assemblies contain gear reducers with ratios that vary according to the model and travel of the jack. If you are ordering a replacement switch assembly, complete information on the jack is required.

CAUTION: Limit switches are not adjusted at the factory. Switches should be set during installation.


(See Image 4 in Figure 1 Below)

Electrical Ratings


DC Current - 115 Volts SPDT, .50 amps - DPDT, .80 amps
AC Current - 115 Volts SPDT, 15 amps - DPDT, 10 amps

10-Turn Potentiometer

0-500 OHM, 2 Watt

NOTE: While the 10-turn potentiometer is rated for 0-500 Ohms, as implemented in the rotary limit switch assembly, it can not and should not operate over its full range. Minimum and maximum resistance values can not be known until the unit is installed and final travel limit adjustments have been made, therefore, the device connected to the potentiometer should include provisions for trimming to compensate for these values.

Wiring Diagrams

Please (See Image 5 in Figure 1 Below)

Figure 1