A quick return mechanism is an apparatus to produce a reciprocating motion in which the time taken for travel in return stroke is less than in the forward stroke. It is driven by a circular motion source (typically a motor of some sort) and uses a system of links with three turning pairs and a sliding pair. A quick-return mechanism is a subclass of a slider-crank linkage, with an offset crank.
During the early-nineteenth century, cutting methods involved hand tools and cranks, which were often lengthy in duration. Joseph Whitworth changed this by creating the quick return mechanism in the mid-1800s.[1] Using kinematics, he determined that the force and geometry of the rotating joint would affect the force and motion of the connected arm. From an engineering standpoint, the quick return mechanism impacted the technology of the Industrial Revolution by minimizing the duration of a full revolution, thus reducing the amount of time needed for a cut or press.
Explain Whitworth Quick Return Mechanism.pdf
The disc influences the force of the arm, which makes up the frame of reference of the quick return mechanism. The frame continues to an attached rod, which is connected to the circular disc. Powered by a motor, the disc rotates and the arm follows in the same direction (linear and left-to-right, typically) but at a different speed. When the disc nears a full revolution, the arm reaches its furthest position and returns to its initial position at a quicker rate, hence its name. Throughout the cut, the arm has a constant velocity. Upon returning to its initial position after reaching its maximum horizontal displacement, the arm reaches its highest velocity.
The quick return mechanism was modeled after the crank and slider (arm), and this is present in its appearance and function; however, the crank is usually hand powered and the arm has the same rate throughout an entire revolution, whereas the arm of a quick return mechanism returns at a faster rate. The "quick return" allows for the arm to function with less energy during the cut than the initial cycle of the disc.
When using a machine that involves this mechanism, it is very important to not force the machine into reaching its maximum stress capacity; otherwise, the machine will break. The durability of the machine is related to the size of the arm and the velocity of the disc, where the arm might not be flexible enough to handle a certain speed. Creating a graphical layout for a quick return mechanism involves all inversions and motions, which is useful in determining the dimensions for a functioning mechanism.[2] A layout would specify the dimensions of the mechanism by highlighting each part and its interaction among the system. These interactions would include torque, force, velocity, and acceleration. By relating these concepts to their respective analyses (kinematics and dynamics), one can comprehend the effect each part has on another.
Breaking the mechanism up into separate vectors and components allows us to create a kinematic analysis that can solve for the maximum velocity, acceleration, and force the mechanism is capable of in three-dimensional space.[3] Most of the equations involved in the quick return mechanism setup originate from Hamilton's principle.[4]
In addition to the kinematic analysis of a quick return mechanism, there is a dynamic analysis present. At certain lengths and attachments, the arm of the mechanism can be evaluated and then adjusted to certain preferences. For example, the differences in the forces acting upon the system at an instant can be represented by D'Alembert's principle.[6] Depending on the structural design of the quick return mechanism, the law of cosines can be used to determine the angles and displacements of the arm. The ratio between the working stroke (engine) and the return stroke can be simplified through the manipulation of these concepts.[7]
A quick return mechanism is an apparatus to produce a reciprocating motion in which the time taken for travel in the return stroke is less than in the forward stroke. It is driven by a circular motion source (typically a motor of some sort) and uses a system of links with three turning pairs and a sliding pair.
The crank and slotted lever quick return mechanism convert the rotary motion into reciprocating motion. It is the inversion of a single slider crank chain. This mechanism consists of two strokes cutting stroke (forward stroke) and idle stroke (return stroke).
A quick-return mechanism is a subclass of a slider-crank linkage, with an offset crank. Quick return is a common feature of tools in which the action is performed in only one direction of the stroke, such as shapers and powered saws because it allows less time to be spent on returning the tool to its initial position.
This mechanism is called a slotted lever quick return mechanism and it drives a horizontal ram that reciprocates in the guide ways provided on the top surface of the machine frame. In the front face of the ram, a tool post is fitted. This is a very special kind of tool post.
"@context":" ","@type":"FAQPage","mainEntity":["@type":"Question","name":"What Is the Quick Return Mechanism?","acceptedAnswer":"@type":"Answer","text":"A quick return speed mechanism is used in the shaper and slotter machine in which the circular motion is converted to reciprocating motion so that the slider moves forward and backward. In the forward direction, the cutting process occurs when there is no such cutting in return.","@type":"Question","name":"Types of Quick Return Mechanism:","acceptedAnswer":"@type":"Answer","text":"An accelerated return mechanism is a mechanism that produces a reciprocal effect so that the system has less time to return stroke when compared with the forwarding stroke. In the quick-return mechanism, a circulars movement like the crank & lever mechanism converts to reciprocating movement, but the return time is different from the forward moment. In many applications, this process is used. Some of them are shaper, slotters, screw-press, mechanical drive, etc. The time required for cuttings is reduced with the help of a quick accelerating mechanism.\n\nThere are three types of quick return mechanisms:-\n\nHydraulic Drive.\nCrank and Slotted Link Mechanism.\nWhitworth Mechanism.","@type":"Question","name":"Applications of Quick Return Mechanism:","acceptedAnswer":"@type":"Answer","text":"These are the following applications of the quick return mechanism:-\n\nIt is used in the shaper machine to flatten the workpiece.\nSlotter and Planer are used the same in machines.","@type":"Question","name":"Advantages of Quick Return Mechanism:","acceptedAnswer":"@type":"Answer","text":"These quick withdrawal mechanisms have advantages:-\n\nThe process is automated.\nThe construction of the system is not so complicated.\nIt can perform operations such as cutting, leveling and slotting the workpiece.\nIdle time is reduced due to rapid return stroke.","@type":"Question","name":"Disadvantages of Quick Return Mechanism:","acceptedAnswer":"@type":"Answer","text":"Disadvantages of the quick return mechanism are:\n\nIn the returning strokes, there is no contact with the work, so there is no cutting, so the process takes longer to complete.\nForward stroke takes longer than return stroke.\nIt takes more power to perform the operation.\nThere is friction in the slider & piston."]
There are different possibilities to make inversion for a Single Slider Crank Chain Mechanism. But for now, we will be discussing the most important inversions of Single Slider Crank Chain. Following are the different Inversion.Bull Engine (Pendulum pump)Oscillating cylinder engineRotary internal combustion engineCrank and slotted lever quick return mechanismWhitworth Quick return mechanismBull Engine (Pendulum pump)In this mechanism, the inversion can be obtained by fixing the sliding pair.Bull Engine (Pendulum pump)As you can see the schematic representation of the bull engine or the pendulum pump above. When the crank rotates then the connecting rod oscillates about the pivot point A. The piston attached to the piston rod will reciprocate.Oscillating cylinder engineAnother Inversion of the single slider crank chain mechanism can be obtained by fixing the turning pair.
In this type of Inversion of Single Slider Crank Mechanism also one turning pair is fixed as shown in the below fig.Crank and slotted lever quick return mechanismThis mechanism is used mostly in shaping machines and slotting machines and rotary internal combustion engines. As you can see from the above schematic representation of the crank and slotted lever mechanism, there will be a slotted bar which is fixed at one and at A. And also connected to the crank by the slider at B. As you can see the other end(P) of the slotted bar is connected to the ram of the machine where the tool post holds the tool. As the crank rotates, the slotted bar starts to oscillate forward and backwards. The name quick returns represent that when the slotted bar moves backward direction, it will be quicker than the forward movement. As it should travel the angle α while backward movement instead of the forward movement β. In the quick return mechanisms always α 2ff7e9595c
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