A push solenoid is an electromagnetic device designed to supply linear motion away from itself. This is in contrast to pull solenoids, which supply their linear motion inwards or towards the solenoid coil. Both types work on the same principle with an electrically-energized wire coil generating a magnetic field that attracts a ferrous metal plunger. The movement of the plunger supplies the motion used by the solenoid to actuate valves or machine parts. The push solenoid is used in many of the same applications as the more common pull solenoid, but finds particular favor in roles that require a percussive action.
Solenoids are very common actuation mechanisms that see wide use in a host of industrial, manufacturing, and automotive industries. They are simple devices with a minimum of moving parts that rely on the generation of a magnetic field to generate the work that they supply. This action is achieved when a wire coil with a hollow core is energized by an electric current, creating a strong magnetic field. A plunger made of a ferrous alloy that is located close to the opening of the coil is attracted or drawn into the center of the coil by the field. This plunger is attached to a linkage, which, in turn, actuates or switches the device connected to the solenoid.
The most common type of solenoid is the pull solenoid, which is designed to supply the working motion inwards towards the coil. The push solenoid is the less frequently encountered variety of solenoid and differs from pull solenoids in that the duty cycle is performed away from the coil and not towards it. In reality, both types work in exactly the same way, and it is only the plunger design and configuration which differs. The push solenoid plunger is simply longer and often made up of two metals, one ferrous and the other not. The ferrous part of the plunger is pulled towards and into the coil just like the pull example, but, owing to the extension on it's opposite end, the working movement is directed away from the coil.
The push solenoid is used in many of the same types of applications that use pull types. More often than not, machine design and space issues will be the sole reason for using one or the other solenoid type. They are, however, particularly useful and are used exclusively where a percussive type of action is required.