Whitworth quick return Mechanisms - Download as Powerpoint Presentation .ppt /.pptx), PDF File .pdf), Text File .txt) or view presentation slides online. A presentation on the whitworth quick return mechanism, that covers the historical tvnovellas.info This work aims to propose a novel design for quick return mechanisms, and the new mechanism is Dwivedi  used the Whitworth mechanism to constructing.
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PDF | Quick-return (QR) mechanisms feature different input durations for Slider -crank QR mechanisms: (a) offset slider-crank, (b) crank-shaper, (c) Whitworth. The Whitworth Quick Return Mechanism, "MBM2", is a mechanism able to transform circular movement into reciprocating movement. It is made of aluminum and. Whitworth quick return motion mechanism: This is first inversion of slider mechanism, where, crank 1 is fixed. Input is given to link. 2, which moves at constant.
In a shaper, the rotary movement of the drive is converted into reciprocating movement. It is done by the mechanism contained within the column of the machine. The ram holding the tool makes the reciprocating movement. In a standard shaper, metal is cut in the forward cutting stroke, while the return stroke goes idle and no metal is cut during this period. To reduce the full machining time it is important to reduce the time taken by the return stroke. The shaper mechanism should be so designed that it can allow the ram to move at a slower speed during the forward cutting stroke. The reciprocating movement of the ram and the quick return mechanism of the machine.
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No notes for slide. Whitworth Quick Return Mechanism 1. Hydraulic shaper mechanism In this type of shaper machine mechanism, the ram is moved forwards and backwards by a piston moving in cylindrical placed under the ram. The machine is consists of a constant discharge oil pump, a cylinder, a valve chamber and a piston.
The Piston-rod is bolted to the ram body. As shown in the figure. Arrangement and working The oil under high pressure is drawn from the reservoir. The oil is passed through the valve chamber to the right side of the oil cylinder exerting pressure on the piston.
This cause the ram connected to the piston to perform forward stroke. Any oil present on the left side of the cylinder is discharged to the reservoir through the throttle valve. At the end of a forward stroke, the shaper dog hit against the reversing lever causing the valves to alter their positions within the valve Chamber.
Oil under high pressure is now pumped to the left side of the piston causing the ram to perform return stroke. Oil present on the right side of the piston is now discharged to the reservoir.
At the end of the return stroke, another shaper dog hits against the reversing lever altering the direction of stroke of the piston and the cycle is thus repeated. The quick return is affected due to the difference in the stroke volume of the cylinder at both ends.
The left-hand end being smaller due to the presence of the piston rod. As the pump is a constant discharge one, within a fixed period, the same amount of oil will be a pump into the right or to the left-hand side of the cylinder.
This will mean that the same amount of oil will be packed within a smaller stroke volume causing the oil pressure to rise automatically and increasing the speed during the return stroke.
The length and position of stroke are adjusted by shifting the position of reversing dogs. The cutting speed is changed by controlling the throttle valve which controls the flow of oil. When the throttle valve is lost the excess oil flow cut through the relief valve to the reservoir maintaining uniform pressure during the cutting stroke. Automatic Table feeding mechanism of shaper The automatic feed mechanism of the table is very simple.
This is done by rotating a ratchet wheel, mounted at the crossfeed screw. This enables a corresponding equal rotation of the crossfeed screw after each stroke.
Arrangement of parts It consists of a slotted disc, which carries a T-slot, as shown in the figure. In this slot is fitted an adjustable pin and to this is attached a connecting rod. The other end of the connecting rod is attached to the lower end of the rocker arm of the pawl mechanism.
The rocker arm swings about the screw C, and at its upper end carries a spring loaded pawl, as shown.
Working Note, that the lower end of the pawl is bevelled on one side. This arrangement helps the power feed to operate in either direction, but the same should be set to operate during the return stroke only. If otherwise, the mechanism will be subjected to a severe stress.
In some latest types of shapers, can driven feed mechanisms are provided which are more efficient and provide a wider range of feed.
Variation in the feed can be provided by varying the distance R between the disc centre and the centre of the adjustable pin. Larger the said distance greater will be the feed and vice versa.
The amount of feed to be given depends upon the type of finish required on the job. For rough machining, heavier cuts are employed, and thus, a coarse feed is needed. Against this, a finer feed is employed in finishing operations. The slotted disc at its back carries a spur gear which is driven by the bull gear. As the disc rotates through this gear the adjustable pin, being eccentric with the disc centre.
This causes the connecting rod to reciprocate.
This, in turn, makes the rocker arm to swing about the screw C to move the pawl over one or more teeth.