Abstract: The project consists of locking the reverse wheel such that it will constraint the reverse motion of the vehicle with the help of ratchet and pawl mechanism. The movement of the pawls will be controlled with the help of the linear actuators. A push button will be provided on steering of the vehicle which will be operated by the driver on choice. Keywords: Ratchet, Pawl, Actuators.I.
INTRODUCTIONThe present invention in a preferred embodiment provides systems and methods for preventing a vehicle from reverse movement on a slope. The system comprising ofa) A heavy commercial vehicle.b) A ratchet and pawl device connected to at least one wheel of the vehicle.
c) A connecting or fastening component which connects the ratchet and pawl device such that the wheel shall rotate only if the ratchet and pawl device rotates.d) And electronic mechanism i.e Actuator which will control the movement of the pawl while engaging or disengaging the mechanism Where in the system may be engaged using an engaging mechanism when reverse motion is undesirable or to be restricted, and may be disengaged when the reverse motion is desirable and is to be.II. BACKGROUND OF THE INVENTIONBrake is the indispensible part of automobile vehicle without which the automobile vehicle is incomplete. It also acts as safety device to the vehicle to control its unwanted motion.But when the brakes are apply all the wheels of the vehicle gets locked ie the vehicle will not be able to move in forward as well as in the reverse direction. This is considerable only when our intention is to stop the vehicle but when moving on gradient roads such as ghats that time the reverse motion is to constraint to provide safe ride to driver as well as to other vehicles on the roads.
So to overcome the problem associated with the brake ie. It locks all the four wheels of the vehicle, we have design such a concept that it will allow the motion in forward direction only thereby constraining the reverse motion of the vehicle. The concept consists of Ratchet and Pawl mechanism. This mechanism will be mounted on rear side of the vehicle such that the ratchet will have the drive with the rear wheels of the vehicle. III. COMPONENTSRatchet and Pawl:A ratchet consists of a round gear or linear rack with teeth, and a pivoting, spring loaded finger called a pawl that engages the teeth. The teeth are uniform but asymmetrical with each tooth having a moderate slope on one edge and a much steeper slope on the other edge.
When the teeth are moving in the unrestricted (i.e., forward) direction the pawl easily slides up and over the gently sloped edges of the teeth, with a spring forcing it (often with an audible ‘click’) into the depression between the teeth as it passes the tip of each tooth.
When the teeth move in the opposite (backward) direction, however, the pawl will catch against the steeply sloped edge of the first tooth it encounters, thereby locking it against the tooth and preventing any further motion in that direction.a) Ratchet and PawlA. Actuators:A linear actuator is an actuator that creates motion in a straight line, in contrast to the circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in many other places where linear motion is required. Hydraulic or pneumatic cylinders inherently produce linear motion. Many other mechanisms are used to generate linear motion from a rotating motor.Electro Mechanical Actuator:Electro-mechanical actuators are similar to mechanical actuators except that the control knob or handle is replaced with an electric motor.
Rotary motion of the motor is converted to linear displacement. There are many designs of modern linear actuators and every company that manufactures them tends to have a proprietary method. The following is a generalized description of a very simple electro-mechanical linear actuator.b) ActuatorMechanism consists of Ratchet and Pawl arrangement which will be mounted on the rear axle of the vehicles or any other location which will have the drive along with the motion of the wheel. One push button will be mounted on steering wheel or dashboard which will be operated by the driver on choice. On pushing the button the pawl will came in engage position with the ratchet and will constraint the reverse motion of the vehicle.
C) CAD diagram of actual workingThe above shown is the CAD diagram of the mechanism. The working of the mechanism can be clearly understood from the diagram. The Ratchet ( shown in red colour) is mounted on rear axel of the vehicle. The Pawl ( shown in orange colour) is just above the Ratchet will be engaged and disengaged with the Ratchet with the help of linear actuator as shown in the figure.
The electric supply to the actuators will be given with the help of 12V DC battery, due to this the actuator will be reciprocated in and out. The output of the actuators is connected to the common link from the two Pawls. When outlet shaft of the actuator say moves inward, the pawl will rise ie disengagement will take place and the vehicle will be able to move in both the directions viz forward and reverse direction. Now exactly opposite to this when outlet of the actuators will move outward and the pawl will fall and engagement will take place. Now the reverse motion of the vehicle will be constraint ie now the vehicle will not move in the reverse direction it will only move in forward direction.
N this way engagement and disengagement of Ratchet and Pawl will take place with the help of push button provided on the steering wheel of the vehicle.Design CalculationsP=W×9.81×Cos45 =20,000×9.81×Cos45 =138.7343×10^3 NConsidering 4 Ratchet and 4 PawlP=138.7343×10^3/(4×4)P= 8.67×10^3Transmitting TorqueT= P×C.G = 8.67×10^3×1000T= 8.67×10^6 N-mmNow, Assuming ? No of teeth (z)= 20