by American Actuator, LLC           

This sales manual is intended to give understanding of American Actuator’s actuators design and applications. We have tried to give as much specific data as possible and if further data is needed we are always happy to accommodate you.

  Design:

The actuator is a complete hydraulic system built into one compact unit, which is hermetically enclosed. It is basically not serviceably only motor can be serviced. The unit is filled at factory with oil and need not be changed or serviced. The following is a brief description of the actuator.

   
         Electric Motor:

The electric motor is directly mounted on the end cap of the actuator with two tie bolts. The motor is of type permanent magnet (PM), direct current (DC) and is available in different sizes as well as for different voltages.

The actuators performance is normally limited by the electric motor for maximum force and as well for duty cycle. This is explained in some depth under “applications”  

Hydraulic Pump:

The hydraulic gear pump is of bi-rotational type, depending on rotational direction the pumps output flow is either out of port “A” or “B”. If motor is not running the ports “A” and “B” are blocked and no fluid will be able to pass. Due to semi soft seats for the built in check valves the leakage is practically zero. The pump is held in place in the end cap by a nut and the drive shaft is directly coupled to the electric motor.

Hydraulic Cylinder:

The end cap is functioning as the end cap for the built in hydraulic cylinder. The cylinder tube is out of steel (1020) and is drawn to extra smooth inside. The piston in the cylinder is of aluminum and is threaded to the rod and locked by anaerobic. The rod is of 75000-psi tensile steel ground and polished. The surface of the rod is also “Nitrotec” processed which gives a very hard surface as well as very good corrosion resistance. The piston seal is Teflon “glyd-ring” and the rod seal is double lip u-cup of polyurethane with the addition of a wiper seal. All seals of industrial grade and is expected to last for the life of the actuator. All dynamic seals have been chosen to reduce friction and slip stick in order to reduce noise and vibrations.

Oil reservoir:

The oil reservoir is concentric with the hydraulic cylinder and is also the structural member holding the end cap together with the rod end cap. The reservoir tube is rolled into grooves in the caps and o-rings function as seal. The reservoir is filled with oil to 60 % of its volume with Exxon Univis J26. There is no vent in the oil reservoir.

Function:

The actuator has three modes: Extend, Retract and Hold. 

Application:

Electric motor considerations:

The electric motor is deciding the performance of the actuator. It is therefore important to understand the performance of the motor. Also it is important to understand that there is no relief valve in the system. Instead the motor should be controlled to limit the output of the actuator.

In order to better understand the relation between motor and actuator performance an understanding of the electric motor characteristic is important. The electric motors output is dependent on the output torque and the speed. As the torque raises the speed goes down, with other words the higher the load is the lower the speed is. Also the higher the torque is the higher is the current draw of the motor. The torque of the pump is directly proportional to the pumps output pressure and therefore the current draw of the motor is proportional to the pressure of the pump. The pressure of the pump is also proportional to the force of the actuator. Hence by limiting the current draw of the motor the pressure/force of the actuator can be limited.

The current limiting device can be a simple fuse, automatic resetting fuse or micro- processor controlled current limiter. If no current limiter is used the actuator will increase the force until the motor stalls. At stall of an electric motor current rush through at a very high rate and the motor will burn in a short time. It is therefore important to have some sort of current limiting device controlling the motor. Conventional systems have a relief valve, which will cause the motor to run against the max load until the motor is stopped. This situation is as prone to burn the motor as running the motor to stall even if the time running against relief valve can be longer without damage to the motor. There is no question that a system with a current limiting device is superior to a system with just a relief valve as it will protect the weakest link, namely the electric motor.

The voltage to the motor will affect the speed of the motor and therefore the speed of the actuator. The higher the voltage the higher speed will be. In battery operated system it is important to consider the voltage under high loads/current. A battery will not supply the rated voltage at high current. The higher current draw out of the battery is the less voltage the battery will supply to the electric motor. The size and type of battery is deciding the voltage drop. A voltage drop at highest load of 10% on nominal voltage is acceptable and an over voltage of 15% is acceptable.

The motors for the actuator are for intermittent use only. The motors are running at very high load for their size so they will burn at prolonged running. They must be run within the duty cycle given and they must be given time to cool down in-between cycles. For each motor we have provided a duty cycle curve, which gives time vs. current over a period of 5 minutes. What this means is that over a five minute period the motor is able to run one cycle at the specified current and time and it can be repeated each five minutes.

Motors available:

The following motors available at this time. Special with other performance and duty motors can be obtained.

Attached are the performance sheets and duty sheets for each motor.

1. Standard motor D1 (12 and 24 Volt DC) identification (#108)
2. High speed motor D2 (12 and 24 Volt DC) identification (#109)
3. Standard motor 90 Volt DC A1 for use with 110 Volt AC
4. Standard motor D4 (12 and 24 Volt DC) with hex shaft at rear end.
5. High power motor D3 (12 and 24 Volt DC)

Orientation:

It is important to understand orientation of the actuator. The suction port is located in the end cap at the bottom (top is indicated by a label). It is important that this port is under oil level at all times.

Standard orientation is horizontal to motor down (see figure below).  

For orientation other than standard an inverted type is available which is suited for application with motor up (see figure below). 

Load control:

As in all systems with pilot operated check valves the load has to be controlled so that the there is always pressure to hold a pilot operated check valve open during operation in order to avoid chattering. The normal way of solving this is to have a throttle valve in the circuit and this is also possible to do in the actuator. For this purpose there is a special pump cap called 3002 to be installed on the pump. This has to be done at assembly so it is important to know when and where this device needs to be used.

The 3002 cap needs only to be used in application where the pull or push on the rod is over 300 lbs.

Pushing load:  use 3002-B

Pulling load:  use 3002-S

Over-center load (both pull and push occurs during the stroke):  use 3002-B+S

When using the 3002 cap the minimum current draw will be approximately 18 Amp (at 12 Volt half at 24 Volt) in the direction of the load.

Note: An actuator can be retrofitted with the 3002 cap but it must be done at the factory.

Mounting:

The actuator has a trunion mount consisting of two opposed threaded holes 3/8-16 UNC, 0.375 deep and a spot-face diameter 0.625. The trunion bolts must be of shoulder type where the shoulder it supported by the spot-face.  

It is most important that no side loads is applied to the rod of the actuator. Align the rod accurately and make sure that the orientation of the mounting axis is parallel to each other.  

Do not try bolts without shoulder and do not use more thread engagement than 0.375”.

Temperature influence:

The actuator is designed to work in a temperature range of –20 to 120 deg F. It will work with diminished performance from –30 to –20 and 120 to 150 deg F. At low temperatures the speed will be reduces and the current draw will go up and at high temperatures the actuator will loose speed and force but the current draw will stay constant.

At large temperature fluctuations the rod will move slightly. This is not an indication of any malfunction in the holding capability of the actuator.

  Buckling:

The rod has a limitation in pushing load capability. At a certain load the rod will buckle.  The chart below shows the limitation in pushing load for actuators with different strokes. The figures are valid for fully extended rods and the load c[ability raises with lesser stroke. In order to improve buckling loads a spacer can be installed in the hydraulic cylinder limiting the stroke.

Stroke Limitations:

The actuators can be made for strokes up to 47.5” down to 4”. This limitation is due to machining capabilities.

  Corrosion:

The actuator is made from aluminum with the exception of the rod, which is steel with Nitrotec processing, which gives superior corrosion resistance. The electric motors exposed areas are made from steel and zinc. Note that the motor is not sealed and must be protected from water.

  Electrical system:

The manual for the actuator gives ideas and instruction how to design the electrical system. It is important that the motor be protected from currents higher is allowed. Also consideration must be taken to the limitations based on duty. This is important in systems where the actuator goes against a physical stop.

Wiring must be designed so that the motor under load will not see less than 90% of nominal voltage. Low voltage will reduce the speed considerably and also limit the max force of the actuator. Special considerations have to be taken to systems driven by a transformer. The transformer must give at least 90% of nominal voltage at max load on the actuator. It might be preferred to use a battery with a charger in favor of a transformer.

For actuator with 90 volt motor supplied by a rectifier it is a good idea to have a current limiting relay before the rectifier (AC side). There are many different types of current limiting relays on the market suitable for this application. Also make sure the rectifier is capable to supply the current required.

  Application data sheet:

“The application data sheet” must be completed and attached to each order of a new application of an actuator. If not completed American Actuator will not take any responsibility for the actuators function in the application.