In this unit you will be learning about Fluid Power Schematic Diagram and at the end you should be able to describe the purpose of Schematic Diagram, you should be able to identify the components on a diagram, and you should be able to use a Schematic to understand how hydraulic circuits work. [NOISE] Hi. That was me at the wheel of a Toro Ground Master 4300 commercial mowing machine. Cutting a 2.3 meter wide swath of lawn at a Torro test facility South of Minneapolis. You can see the Torro Ground Master mower in this slide. It has five mowing decks that are individually articulated, so they can follow uneven ground. All the decks also have to lift off the ground. It's a hydraulic machine with a dry system, the steering wheel, the cutting blades, and the deck lift all hydraulically actuated, and run by a 33 kilowatt diesel engine. The reason why hydraulics is used in a machine like this, is that the fluid power can be pumped through flexible hoses to each one of those decks, and to the deck lift without the need for complex mechanical linkages. Further the hydraulic drive and stern wheel are a rugged, and reliable solution for machines such as this one. I'll be using this machine to explain the concept of fluid power schematics, which are a graphical diagram with symbols that describe the function, and the inner connections of the hydraulic components that make up a system. It's important they become familiar with fluid power component symbols, as we'll use them constantly in this course. Here's the schematic for the GM 4300, a link is on the resource area of the course, so that you can study the schematic on your own which I recommend that you do. While it may look complex now. Shortly, you'll be able to interpret diagrams like this, and understand how a fluid power machine operates. First I'll introduce a few of the basic symbols. Then, I'll walk through the GM 4300 schematic. The schematics that we draw in this course were made with Microsoft Visio, which has a fluid power parts library, but other drawing packages can be used as well. First let's go over some of the line types. In this diagram, the working lines, which are the solid lines. And they can either be pressure lines, such as this one coming out of the pump, or return lines going back to the reservoir. Dash blinds, which you see on this diagram, can be control lines such as this pilot line on our relief valve, or this line coming out of a motor that goes back to the reservoir which is a drain line. Here's the diagram for a cylinder, that has the basic components of a cylinder indicated. So it's got, parts that indicate the piston, the rod, and then two ports because in this case it's a, bi-directional cylinder that can go in two directions. In the video coming up, I'm going to show you that the cylinders are used to raise and lower the mowing decks on the Toro GM 4300, and I'll be operating the controls on the machine to raise and lower the decks. And then as the camera zooms in. You can see the lift cylinders operating. [NOISE] Here's a closeup of the center front mower deck, with the arrow pointing to the cylinder, and if you look closely on top of the cylinder, you can see the. Two hose connections that go to the cylinder, and that's because this is a double acting cylinder, that has to both raise and lower the deck. Now we're back to the full schematic for the machine. And I've circled in red, the five cylinders that raise and lower the five mowing decks. And then in the next slide we've zoomed in so you could see those cylinders clearly, and notice that each cylinder has two ports attached, because they are bi-directional cylinders, because that deck has to both go up and go down. So I'll let you on your own, trace through that full schematic to see where the two lines come from for the five cylinders. Rotating components are indicated by circles, and the triangle in the circle points in the direction of the flow, so the one that you see here is a pump. For a triangle that points the other way, it indicates a hydraulic motor. And there are embellishments that you add to the schematic symbol, in order to indicate specific features of the pump. So, I'll go through a few of those. So here's one that show the pump is bi-directional, that is the pumps in two directions. Nest we have a arrow that going through the symbol which indicates the pump is variable displacement, and that control can either be. Through a manual lever or it can be through a through a power control or it can be through an electronic control. But it all cases, it controls the displacement of that pump. Another embellishment that you can add to the symbol is, an indication of the power input. So, that shaft symbol sticking out on the right shows. The motor, either a diesel engine or electric motor that's driving the pump. And then the last one I got here shows a case drain. And that's because hydraulic motors and pumps leak fluid through their seals, and it collects in the case, and there has to be some place for that fluid to go. So on many pumps and motors there's a case drain that takes that fluid back to the reservoir, and you notice that it's indicated with a dotted line to indicate case strain. Here's a picture of the mower blade underneath that Torro mowing machine. And then if we look on top of the deck, that blade is operated by a hydraulic motor. And you can see, if you look at the motor, the two big thick hoses, going in to the motor, are the hydraulic lines, going in, and one going out. And then if you look closely, on top of the motor, you'll see a smaller hydraulic line, coming out of the motor, and that's that case drain that's taking the leakage fluid back to the reservoir. Now here we are, back to the full schematic to the mowing machine. And as I've indicated before, there's five of these mowing decks. And I've put a circle around the five motors, one driving each one of the five decks. Here we are zoomed in around one of them. This is motor number 5. And you can see a few things about that. Motor schematic indication, first notice that it is a, a motor because the triangle pumps points in. And then notice that it's a one way motor, because we just have one triangle. You can see the indication of the shaft, so that'll be the shaft that goes down to the motor blades. And then you can see that dash line, which is the case drain of the mower. If you look over on the right hand side of the schematic, it's got some specification, so if you follow down that table down to 2 and 5, you can see that this is a 17.16 cubic centimeter per revolution. Fixed displacement motor, and it's fixed displacement because there isn't an arrow through it. Okay, now let's take a look at some of the schematic indications for Valves. The basic symbol for a Valve is a rectangle. Arrows are added to show the flow direction of the fluid, and boxes are added to show multiple positions of the Valve. The one I have on the diagram is a pressure relief Valve, which is put into a circuit to avoid overload conditions. So here, I've labeled some of the components, so it's got an input line and an output line. And then, the flow path is indicated by the arrow. And then, the dash line is a pilot line, so that pilot line, notice how it's connected to the input side. And, the way that it works is that if the input line gets over a certain pressure, then the pilot line. Forces the Valve into the other position. So now the central arrow is lined up with the inlet and the outlet, and then, flow can go from the inlet to the outlet, which in this case, the purpose is to relieve the pressure in that inlet. So and then finally the arrow on the right, indicates that this particular pressure relief Valve. Is an adjustable Valve, so you can set the pressure with which it triggers its action. I'll let you go back to that full schematic for the mowing machine, and on it you'll find several different pressure relief Valves. Now let's take a look at Directional Control Valves. There's one box that indicates each position of the Valve, so this is a three position Valve. And then, there are four lines that connect to this Valve, so this is a, a four way Valve as well. So let's take a look at the, the middle position. And the middle is always drawn where the Valve is at it's neutral position. So, the four lines in this Valve. One, the P indicates the pressurized line. The T indicates the tank line or the reservoir line so it's a low pressure one, and then the two outputs are, are A and B. So in this middle position, there's no connection between any of the ports which means the Valve is essentially in a completely off, or closed, position. If you actuate the valve, and slide it to the right, then you can, kind of, see that from the directions of the arrows, that the P is connected to the A line, and the B line is connected to the T. So that would put the pressurized fluid to the A line, and the return line would be B. And then if you switch over and actuate the valve in the other direction, then the flow paths are reversed, so now the pressure will be going to the, the B Valve. Let's take a look at how that might work in a, in a circuit. So, here's an example of a Directional Circuit. Over on the left, we've got a pump that's connected to the reservoir, so it's pumping fluid out of the reservoir. We got a pressure relief valve over here in case the pressure in this line gets too high, then the relief valve will open and bring the fluid back into the reservoir. Then we've got our Directional Control Valve. And then it's actuating a cylinder. So this is, you know essentially this circuit of a log splitter, that you'll see in another unit in the course. And the purpose of the circuit it has a cylinder, be able to go in one direction. In this case up. Or able to go in the other direction. So with the valve in the current position then everything's off, the cylinder not going to move. If you switch the valve in the down position then the pressurized line will come through and into this part of the cylinder, cylinder will go down. Then if you reverse and flip the directional valve up, then the lines will be reversed. Now the pressurised line will go into the other port of the cylinder and the cylinder will go up. If you take a look at that full schematic for the mowing machine, see if you can spot Directional Control Valves on the schematic because there are several. Now that you have the basics, I'm going to briefly talk your way through the whole Mower Schematic. I'm going to go fast, so what you'll want to do is to study that schematic on your own. So let's take a look section by section. The section that I'm circling right now is the drive section, which is a. Form of a hydrostatic transmission that you'll learn about in other parts of the course. But here's a pump, which is being driven off a drive shaft of the diesel engine of the mowing machine, and it goes to the one, two, three, four motors with one motor attached to each one of the drive wheels on the mowing machine. So that's the drive section. Up over here we have the section that lifts the mowing decks up and down. We covered that before, so here are the five cylinders. And if you trace through the schematic, you'll see that here's a pump that's connect to the drive shaft that again comes off the diesel engine pumps fluid out. And then if you follow it around, it goes into the section of the, the dick the deck raising, and it gets there through a directional control valve that raises, enables the cylinders to go in both directions. So you can raise and lower the decks. Then over on the right, which is fed. Here's another pump that supplies pressurized fluid over to this section on the right. And this is the whole steering circuit which has the steering wheel up here, and then the directional control valve, and then there's a steering cylinder down underneath. So we'll take a look at a picture of that in just a little bit. Then finally down on the lower left, we have those five deck mowers, and if you trace through the schematics, so for there's two pumps that supply those. One of the pumps supplies the two rear mowing motor decks. And the other pump supplies the three in the front. So, let's just take a look at that line. So here's the, the motor that supplies pressurized fluid. The fluid comes down, passes along. And then the three mower motors are connected in series. So the fluid goes in one, and out one, in the center, out the center. And then in the other, and out the other. And then it goes back, and it goes through a cooler, which is this indicator, to just take some of the heat off the hot oil. And then it goes through a filter to take out the particles, and then it goes back into the reservoir. We'll close out the video, with a short video where I'll walk you through that circuit on the machine. And the reason why these three are connected in series, is that they all get the same flow and that means that all three motors turn at the same speed. And that's really important to maintain consistent cutting speed between all the decks, to give you a nice uniform cut of the lawn. Before we get to that video I'm just going to show a few pictures of, under the hood of that mowing machine, so you can see where the various components are. So here we've got the the case opened on the mowing machine. And we're going to zoom in right to this area. Well, let's see, first here's the that diesel engine that runs the whole machine. And then, let's take a look in this area. So that's what the next exposure is, here's that diesel engine over on the right. And then over here are the five hydraulic pumps that you can find in that schematic diagram. So the, the first one here is the pump that runs a hydrostatic transmission for the dry circuitry, and then two, three, four, five are the five smaller pumps that run the. The deck lifts and the, and the mowing motors. Here's a picture of the rear of the machine on, on this case, the, the rear wheels that steer on the mowing machine. So you can see the wheels and then here is the steering cylinder, with this two hoses coming in that cause the rear wheel to turn to give you steering. And then the other thing to notice are these two lines which are the hoses going into the hydraulic motor, which is the drive motor on the right rear wheel. Then we have the back of the machine. What you see on the back is a radiator. That water cools the diesel engine but the, the bottom half of the radiator cools that hydraulic oil. So that's that return oil that comes from the various motors, which the oil is hot and the heat exchanger in the back helps to get rid of some of the heat from that oil. [SOUND] So let's trace the fluid, flow it through the front deck, so it comes out of the valve block, through this rigid conduit, and then down through the flexible conduit into the first motor. Back out the first motor. Through the conduits. Turning back, comes out, and into the second motor. And out of the second motor, and out through the third motor. And back. Underneath back into the rear of the engine, where it goes into the cooler.
