Practice Tips #61: Foot Controls (not just to drive your handpiece).

Practice Tips #61 focuses on the foot control or, more properly, rheostat. It is a key component to your delivery system. Air passes through it when you step on it to drive your handpieces, but this is not all a foot control does.

All foot controls will have one main large (1/4” o.d.) line that feeds air into the foot control. This "ribbed" line appears to have a seam running along the length of the line. This raised portion helps to identify the “air-in” line.

A “standard” foot control has two large lines (as depicted above). The “ribbed” line side brings air into the foot control. The smooth line is for air out when the foot control depresses.

Marus, Beaverstate, DCI, etc. Units:

The air outlet line from the foot control connects to a single large line at the end of the umbilical, which then connects to a routing manifold (#49-83). The routing manifold then splits the drive air to send air to the air coolant adjustment knob, an air signal to the water on/off toggle (and then to the water relay), as well as a line to the drive air port of the handpiece block. So, while stepping on the foot control runs your handpiece (and allows you to control the speed of the handpiece) it also provides the air and water coolant to the handpiece.

A-dec Units:

The foot control has two blocks connected together underneath the foot control dome. The main block drives air-in and out. The secondary block (often called the signal relay) also receives the drive air from the main block and splits it to send a signal through one small line to activate the coolant water. Occasionally it has a second small line for coolant air. Normally, none of these foot control lines are fed through the umbilical. They attach to color-coded lines in the umbilical, which then attach to a manifold in the unit for ultimate connection to the handpiece blocks. Many A-dec units have the manifold mounted directly to the assembly of blocks, depending on the specific model of A-dec unit.

Foot Control With a On/Off Toggle (pictured below):

The additional split of drive air for water activation does not take place at the routing valve in the unit (blocked outlet port). Instead, an extra outlet port on the valve in the foot control feeds through the toggle. It attaches to an extra line in the umbilical (green or green with a black stripe). That feeds directly to the water relay. There is an air activated valve inside the unit that turns the water to the handpieces off and on. This way, the water does not automatically turned on every time the foot control activates. Additionally, there is no water on/off toggle on the unit.

Foot Control With a Button (pictured below):

These have an extra outlet from the main foot control valve that feeds to the button when the foot control activates. This simply changes where the drive air splits. Sometimes the button used for coolant air feeds directly to the block (bypassing the needle valve for a great burst of air through the coolant ports). It can also still be fed through the coolant needle valve to allow for adjustment of flow. A-dec normally uses a green line with a black stripe in the umbilical for coolant air (same as water activation line). Other manufacturers have a tendency to use different colors. Of course, the button can also be used to send a signal to an air activated electric switch for an ultrasonic scaler or electro-surge, etc.

Ultimately, the only difference in all the foot controls depends on where and how the drive air splits. As well as the type of additional on/off control for the split air. For foot controls with accessories and multi-line A-dec units, the split occurs within the foot control. All of the lines are hooked up the same. There is an extra small line for a 3 hole foot control that is always for water coolant activation, unless the foot control has a button. For two-line non-A-dec units, the split is in the unit.

Lastly, there are occasional exceptions to the rules. For example: Beaverstate's two handpiece units tend to have the foot control tubing run directly up to the unit. It attaches to the routing valve directly.

As you have read in Practice Tips #61, the air from the foot control does much more than just drive your handpiece. When replacing your foot control, make sure your foot control is properly configured for your delivery system. If you don't, you will lose key functions.


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