Modifying the design of Pressure Gauge Mechanism for better efficiency, less material and high control
Introduction to pressure gauge
Before we take a look at the project let's first introduce ourselves to pressure gauge.A pressure gauge is a fluid intensity measurement device. Pressure gauges are required for the set-up and tuning of fluid power machines, and are indispensable in troubleshooting them. Without pressure gauges, fluid power systems would be both unpredictable and unreliable. Gauges help to ensure there are no leaks or pressure changes that could affect the operating condition of the hydraulic system.
There are many types of gauge styles, the most common being Bourdon tubes and bellow gauges. Bourdon tubes function by taking the pressure and converting it into mechanical energy. This energy moves a dial in the gauge, displaying the current amount of pressure in the system. Bourdon tube gauges are currently some of the most common gauges and have different configurations such as curved, helical and spiral. The different style of tubing, the size of the tube and the material it is made out of all vary based on the pressure range. One important characteristic to note is the cross section of the tubing changes with increasing pressure. Generally, as the working pressure of the gauge increases, the shape of the cross section of the tube’s design will gradually change from an oval shape to a circular shape.
Bourdon tube operation is simple. They consist of a semicircular and flat tube of metal, fixed at one end and attached to a sensitive lever mechanism at the other. As pressure increases inside the tube, the force of the fluid attempts to straighten out the curved tube. The tube then pulls away from the lever, which being connected to the needle on the display, shows the pressure at the fluid port.
Objective of the project
So around couple of months ago my friend who is working at Bourdon Pressure Gauges PVT. LTD. arranged us an industrial visit in the company. We had to create a report on industrial visit for a subject in our engineering curriculum. So,we went to the company and observed that the pressure gauge mechanism which Bourdon gauges PVT. LTD. were using for production of the gauges had couple of extra components which could be deleted while doing assembly. Thus, minimizing the cost (however little) and minimizing the time for an assembly of the mechanism.
We asked for a single piece of mechanism to be provided us for the project but having strict norms they didn't allow us to take the mechanism. So,we bought the same pressure gauge from the market having 2" dial,cracked it open and started working on it. The above image is an actual representation of the pressure gauge mechanism as CAD Model (Solidworks), we took the pressure gauge mechanism measured every part and made a cad model on trial and error method.The basic principal was measuring how much the Sector gear travels which turns pinion gear which moves the indicator on a dial.
The 2" pressure gauge measures 0 to 150 psi the pinion turns 270 degrees.
The first thing we noticed was for the limiting the rotation of the sector gear the mechanism had a pin and a screw fixed on top plate thus, the sector gear does not rotate out of the pinion gears and always stays in contact. The screw has a slot for the purpose of adjusting the end points of the rotation of sector gear.
The screw surface limit was set on zero,as hair-spring added a torque on the pinion the sector gear stayed on zero indicator of the dial.The main problem came with the pin,as the sector gear continuously strikes the pin for longer period of time it may bend and may go further more than the set end limit.
The screw and pin were additional components applied on the pressure gauge assembly which could be removed for cost cutting purposes. To remove that there should be a provision designed to limit the set rotation of sector gear.
Hence we provided a slot on the existing design of the sector gear shown in below image
Case 1
Case 1
The slot matches the existing location of rivet and the sector gear can move freely in the slot.To limit the rotation of the sector gear the slot can be made smaller but the rotation of the sector must be definite meaning that the distance which it travel should be calculated and should be made standard furthermore the existing design of the assembly remains the same only the dimensions of the die-punch of the sector gear changes and only one die should be made by Bourdon Gauges Pvt Ltd for production of sector gear
The drawback of this design is that the sector gear is now made bigger and does not accommodate in the existing assembly also, the lower part of the sector gear touches the brass block restricting the movement of it as shown in below image
Case 2
Thus a new design must be made which will eliminate the flaws mentioned above.It can be done by changing the design of sector gear, making it compact, but if the design of sector gear changes the dimensions of upper plate and lower plate also changes. thus the design will be completely new and only components such as Rivets, Screws, Pinion wheel, hair-spring, connector will remain intact.all of the other parts changes,such as sector gear, upper plate, Lower plate.
The above image is of complete design of the pressure gauge mechanism designed while using less components and making the design simple.The slot provided is calculated with exact rotation of sector gear which will integrate the rotation of pinion gear which rotates the indicator across dial.
