Diaphragm Type Metering Pumps

This blog will allow you to visually see how a Madden JN series diaphragm metering pump works. We have placed an emphasis on explaining how the 10:1 manual stroke adjustment works.

JN Series Metering Pump Overview


Written Explanation/Video’s Script

To follow along or simply read the explanation, see here….

“Welcome back to another Madden video. Today we will be giving a simple overview on our JN series diaphragm metering pumps with a focus on the operations of the 10:1 manual output adjustment knob.

Here we have a JN111A industrial metering pump ready for testing. John is pouring grade general purpose lubricant into the body of the pump. All Madden metering pumps sit in an oil bath, they’re constantly lubricated and maintenance is minor and simple…. Fill the body until the oil is just over the drive shaft.

This JN111A chemical dosing pump has a wetted end made up of all Teflon materials. It is going to service an application needing to pump 98% sulfuric acid. We also have the double diaphragm setup on this pump for extra protection.

Next we’re showing you the gear box. The different gear ratios inside are the only component that separates the JN101, 102, 104, 105 107 and 111, the worm gear and sprocket rations are increasing or decreasing the motor’s rpm’s to achieve different stroking speeds to the diaphragm. Other than this, the function of every model is the exact same throughout the series.

Now for the manual adjustment knob explanation. Take a look at how the drive shaft and eccentric piece pushes the retainer plate back and forth…. Currently the pump is running at 100%, so in this case it is pumping at 11 GPH. The way the manual adjustment knob affects this is through a loss of motion principle.

Let’s take a closer look.

Inside we have a retainer plate, eccentric and a bearing. If you’re not familiar with an eccentric, for simplicity’s sake, think of its shape similar to an egg. As the eccentric rotates, part of the time it will barely be pushing bearing into the retainer plate… and for part of the rotation it will be fully extending out against the plate. This motion is what pushes the plate and diaphragm forward. For the diaphragm to travel backwards, there is a heavy duty spring between the retainer plate and pump body, which forces the plate and diaphragm to travel back.

So, to turn down, or fine tune a JN series metering pump’s output, we need to restrict the retainer plate’s full range of motion.

We achieve this with a CAM. A CAM is another eccentric or egg shaped object. When the CAM is backed off, or open, as seen in this picture, it allows the retainer plate to fully follow along with the bearing and eccentric for the entire 360 degree rotation. Giving the piston and diaphragm a full stroke. When we turn the adjustment knob down, or close it, the CAM extends forward. This restricts the retainer plate’s motion backwards by a certain percentage. Thus decreasing the stroke length to the diaphragm resulting in a decrease in output.

Now let’s take a look at this while the pump is running.

Here the stroke adjustment knob is at 100, so it is all the way open and the retainer plate and diaphragm will travel freely with the bearing and eccentric…

Now watch as John starts to back off, or close the knob. The CAM is now protruding forwards and keeping the retainer plate from going all the way back. You can see this by the knocking motion of the lid. If the lid were to be fastened, the retainer plate would push backwards for only X% of the eccentric and bearing’s 360 degree rotation, once it hit the CAM the components would separate for a split second as the CAM held the retainer plate from moving any further backwards. Then as the eccentric and bearing come back around, it would push the plate and diaphragm forwards again.
And that completes the explanation of the loss of motion principle as well as concludes our JN series overview.