Heavy Duty Scotch Yoke Actuators

Product Announcement from RSVP Actuators & Controls

Heavy Duty Scotch Yoke Actuators-Image


There are several important considerations for evaluating actuator design and overall performance.

Among these considerations are torque output versus cost and size; effectiveness of seals, ease of mounting and adding accessories.

RSVP 1031 actuators are computer designed to properly balance these criteria and to provide the alternative or combination of alternatives that best fit your particular needs.

Quality, safety, dependability and efficiency are built into every RSVP 1031 actuator.


The body configuration is computer designed to optimize the transmission of force through the piston rod to the torque plug. Sturdy bearing surfaces assure effective sealing and long life through efficient torque transmission. A thrust pin is secured to the piston rod, and a roller is placed over the pin to allow free movement within the slot of the torque plug. This acts to reduce friction and wear. The torque plug has a closed cast slot; it is not open on one end. As a result, there will be no lost motion due to springing open under high torques. Obviously, to obtain maximum efficiency, all tolerances are closely held.

More than economy, efficiency means dependability. For example, the journals of the torque plug provide wide bearing surfaces for ease of rotation. These also resist side thrust and wear caused by possible misalignment in mounting to a valve or damper. The piston rod slides through bronze bearings secured between the body and the cylinder adapter or rod cover. The bearing is designed to minimize friction, but the area is sufficient to counter side thrust and wear.


The RSVP 1031 actuator is designed with three modules. The first module is the center-body. We offer five different sizes of center-bodies; 26, 33, 45, 60 and 80. The second module is the power assembly. The third is the spring assembly. The power and spring assembly modules are removable, serviceable and interchangeable without removing the center-body module from the valve. This procedure does not require any special tools.

1. Body Assembly: Heavy duty modular type body allows every actuator to be made spring return or double acting.

2. Scotch-Yoke: A balanced scotch-yoke mechanism provides optimum torque output and maintenance simplicity by transforming the linear travel of the piston into a 90 degree rotating movement.

3. Thrust Pin & Roller: A thrust pin is secured to the piston rod and rollers are placed over
the pin to allow free movement within the slot of the torque plug.

4. Torque Plug Seal: O-rings are located both top and bottom preventing environments from entering the body housing.

5. Yoke Bearings: Located on both top and bottom of the scotch-yoke, these UHMW polyethylene replaceable bearings allow the actuator to cycle more than any actuator in its class and aid in applications where the actuators are left in one position for years.

6. Stop Bolts with Jam Nuts: These bi-directional travel stops are an integral part of the actuator allowing 80 degree to 100 degree total travel adjustment. Internal travel stops are optional to prevent tampering.

7. Piston Rod: The piston rod is one continuous steel rod made of 1045 steel bar with a hard chrome plating eliminating any side load deflections. This design also allows our maximum operating pressure of 250 psig to apply to all our 1031 actuators.

8. Rod Bearings: These replaceable bronze SAE 660 bearings are secured between the body and the cylinder adapter, or rod cover. The bearings are designed to minimize friction.

9. Rod Seals: This dynamic seal between the rod bearings and piston rod is a molythane
poly-pak seal. The o-rings load the molythane lips for better low pressure sealing. As the pressure increases, the lip loading is increased, maintaining an effective seal. There is also a GarlockTM gasket between the body and the adapter.

10. Piston: Each piston on all 1031 actuators has the option of having two piston seals on each piston. This allows longer life in high cycle applications.

11. Cylinder: The cylinders are finely honed to a very low RMS finish, and then coated with XYLANTM. This bonds to the chemically prepared surface of the steel cylinder so effectively that unlike other coatings, cracking and flaking are virtually eliminated. This fluoropolymer coating is highly resistant to abrasion and thermal shock providing excellent lubricity and low friction properties. Corrosive properties of salts and other chemicals normally found in the atmosphere or instrument air supply system will not adversely affect its performance. Stainless Steel and AmalgonTM cylinders are also available.

12. Spring: Each spring is self-contained and pre-loaded in the cylinder. This prevents any danger when the actuator is serviced and allows for field exchange of springs.