Podcast
Questions and Answers
How much must the speed of the tappet shaft be reduced for a 3/1 twill weave?
How much must the speed of the tappet shaft be reduced for a 3/1 twill weave?
- By 1/2 of the main shaft
- By 1/8 of the main shaft
- By 1/3 of the main shaft
- By 1/4 of the main shaft (correct)
What is the dwell period of the heald frame?
What is the dwell period of the heald frame?
- The time for which the reed is stationary at rear most position (correct)
- The time for which the reed is in motion
- The duration of one full cycle of the heald frame
- The time for which the reed is stationary at maximum position
Which factor does NOT affect the construction of the tappet cam?
Which factor does NOT affect the construction of the tappet cam?
- Dwell period of heald frame
- Stroke of heald frame
- Dia. of treadle bowl
- Speed of the machine (correct)
What does the lift or throw of a cam refer to?
What does the lift or throw of a cam refer to?
What happens as the number of cams increases in a cam shedding system?
What happens as the number of cams increases in a cam shedding system?
What is the relationship between the width of the machine and the dwell period?
What is the relationship between the width of the machine and the dwell period?
At what angle are 8 cams installed on the counter shaft for a weave design of 8 picks per repeat?
At what angle are 8 cams installed on the counter shaft for a weave design of 8 picks per repeat?
What defines the maximum displacement of the heald frame?
What defines the maximum displacement of the heald frame?
What is the primary advantage of using the Hattersley dobby over pegged lattice systems?
What is the primary advantage of using the Hattersley dobby over pegged lattice systems?
What is a key distinguishing feature of the Hattersley dobby compared to the Keighly dobby?
What is a key distinguishing feature of the Hattersley dobby compared to the Keighly dobby?
What is the maximum speed a rotary dobby can achieve according to the information provided?
What is the maximum speed a rotary dobby can achieve according to the information provided?
What role do the locking bars L1 and L2 play in the Hattersley dobby mechanism?
What role do the locking bars L1 and L2 play in the Hattersley dobby mechanism?
What is the main principle behind the operation of the Hattersley dobby?
What is the main principle behind the operation of the Hattersley dobby?
How do the push bars operate in the Hattersley dobby mechanism?
How do the push bars operate in the Hattersley dobby mechanism?
What is the significance of the stop bars S1 and S2 in the Hattersley dobby?
What is the significance of the stop bars S1 and S2 in the Hattersley dobby?
What innovation did the rotary dobby introduce in terms of weaving speed?
What innovation did the rotary dobby introduce in terms of weaving speed?
What happens when the fork lever is moved upward with the clamp screw?
What happens when the fork lever is moved upward with the clamp screw?
Which is a disadvantage of the dobby shedding mechanism compared to crank or cam systems?
Which is a disadvantage of the dobby shedding mechanism compared to crank or cam systems?
What is a key improvement of dobby shedding systems over cam shedding systems?
What is a key improvement of dobby shedding systems over cam shedding systems?
What is the typical position for mounting dobbies in most looms?
What is the typical position for mounting dobbies in most looms?
What classification feature is associated with dobby shedding mechanisms?
What classification feature is associated with dobby shedding mechanisms?
Which of the following is NOT an advantage of the dobby shedding system?
Which of the following is NOT an advantage of the dobby shedding system?
Why might dobby shedding mechanisms lead to fabric faults?
Why might dobby shedding mechanisms lead to fabric faults?
What types of patterns can be produced using the dobby shedding mechanism?
What types of patterns can be produced using the dobby shedding mechanism?
What is the purpose of the auxiliary needle (A) in the Verdol jacquard mechanism?
What is the purpose of the auxiliary needle (A) in the Verdol jacquard mechanism?
How many hooks does the double lift Verdol jacquard utilize for each harness?
How many hooks does the double lift Verdol jacquard utilize for each harness?
What shape are the cylinders of Vincenzi Jacquards made to enhance performance?
What shape are the cylinders of Vincenzi Jacquards made to enhance performance?
What happens if there is no hole for the selecting needle (S) in the Verdol jacquard mechanism?
What happens if there is no hole for the selecting needle (S) in the Verdol jacquard mechanism?
Which format of the Verdol jacquard is commonly used in modern applications?
Which format of the Verdol jacquard is commonly used in modern applications?
What role does the supplementary hook (H) play in the double lift Verdol jacquard?
What role does the supplementary hook (H) play in the double lift Verdol jacquard?
What allows the hook in the double lift Verdol jacquard to move appropriately during the action?
What allows the hook in the double lift Verdol jacquard to move appropriately during the action?
How does the knife K1 contribute to the lifting of the harness in the mechanism?
How does the knife K1 contribute to the lifting of the harness in the mechanism?
What happens to the force in the system as the slope of the cam contour increases?
What happens to the force in the system as the slope of the cam contour increases?
What is the maximum number of cams typically installed on a counter shaft to avoid excessive force?
What is the maximum number of cams typically installed on a counter shaft to avoid excessive force?
In which type of Tappet Shedding are the heald frames returned by an external device?
In which type of Tappet Shedding are the heald frames returned by an external device?
What is a reversing media in the context of Tappet Shedding?
What is a reversing media in the context of Tappet Shedding?
What type of mechanism is used to lower the heald frames in Negative Tappet Shedding?
What type of mechanism is used to lower the heald frames in Negative Tappet Shedding?
What drives the motion of the tappet cams in the described mechanism?
What drives the motion of the tappet cams in the described mechanism?
What is the role of the treadle lever in the Tappet Shedding mechanism?
What is the role of the treadle lever in the Tappet Shedding mechanism?
What occurs when the tappet cam presses the treadle lever according to the mechanism described?
What occurs when the tappet cam presses the treadle lever according to the mechanism described?
What is the purpose of the knives (f) and (g) in the loom's mechanism?
What is the purpose of the knives (f) and (g) in the loom's mechanism?
At what point does the harness remain in the bottom position?
At what point does the harness remain in the bottom position?
What happens when the right-hand solenoid (H) is energized?
What happens when the right-hand solenoid (H) is energized?
Which component is responsible for lifting the harness in the next pick cycle after it was previously lowered?
Which component is responsible for lifting the harness in the next pick cycle after it was previously lowered?
What configuration occurs when both knives (f) and (g) reach their respective limits at point (3)?
What configuration occurs when both knives (f) and (g) reach their respective limits at point (3)?
What continues to happen after the harness reaches the top-most position at point (5)?
What continues to happen after the harness reaches the top-most position at point (5)?
Which of the following accurately describes the initial state of the system?
Which of the following accurately describes the initial state of the system?
What is the role of retaining hooks (d) and (e) in the loom mechanism?
What is the role of retaining hooks (d) and (e) in the loom mechanism?
Flashcards
Tappet shaft speed reduction
Tappet shaft speed reduction
The speed of the tappet shaft needs to be adjusted based on the number of cams used. For example, a 3/1 twill requires a 1/4 speed reduction from the main shaft, and 8-thread sateen needs an 1/8 reduction.
Cam construction factors
Cam construction factors
Cam design is influenced by the weave type, the heald frame's movement duration (dwell period) and range (stroke), and the treadle bowl's diameter and contact point.
Dwell Period
Dwell Period
The time the reed stays stationary at its extreme position, or the time taken for the heald frame to return to its original position. It is related to machine width and inversely related to speed.
Treadle bowl
Treadle bowl
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Cam lift/throw
Cam lift/throw
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Cam repeat size limitations
Cam repeat size limitations
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Cam follower arrangement
Cam follower arrangement
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Cam shaft angle
Cam shaft angle
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Cam Contour
Cam Contour
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Excessive Force (Cams)
Excessive Force (Cams)
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Negative Tappet Shedding
Negative Tappet Shedding
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Positive Tappet Shedding
Positive Tappet Shedding
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Reversing Media
Reversing Media
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Tappet Cams
Tappet Cams
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Bottom Shaft
Bottom Shaft
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Heald Frames
Heald Frames
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Dobby Shedding
Dobby Shedding
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Dobby Shedding Location
Dobby Shedding Location
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Dobby Shedding Advantages
Dobby Shedding Advantages
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Dobby Shedding Disadvantages
Dobby Shedding Disadvantages
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Shed Opening Adjustment
Shed Opening Adjustment
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Shed Height Adjustment
Shed Height Adjustment
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Dobby Shedding Classification
Dobby Shedding Classification
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Dobby Shedding Limitations
Dobby Shedding Limitations
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Hattersley Dobby
Hattersley Dobby
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Keighly Dobby
Keighly Dobby
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Push Bars
Push Bars
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Stop Bars
Stop Bars
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Locking Bars
Locking Bars
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Rotary Dobby
Rotary Dobby
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Dobby Shedding Speeds
Dobby Shedding Speeds
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Double Lift Principle
Double Lift Principle
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Harness Movement
Harness Movement
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Double Acting Knives
Double Acting Knives
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Retaining Hooks
Retaining Hooks
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Solenoid
Solenoid
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Harness Lowered
Harness Lowered
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Harness Lifted
Harness Lifted
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Pick Cycle
Pick Cycle
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Weave Design
Weave Design
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Vincenzi Jacquard
Vincenzi Jacquard
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Verdol Jacquard
Verdol Jacquard
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Double Lift Verdol Jacquard
Double Lift Verdol Jacquard
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Selection Method of Verdol Jacquard
Selection Method of Verdol Jacquard
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Auxiliary needle
Auxiliary needle
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Swing board
Swing board
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Supplementary hook
Supplementary hook
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Supplementary knife
Supplementary knife
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Study Notes
Weaving Mechanisms
- Warping yarns are divided into two layers:
- Top layer is the top shed line
- Bottom layer is the bottom shed line
- The gap between layers is the shed
- Objectives of shedding motion:
- To raise and lower the heald frames carrying the warp yarns.
- To create an opening for picking media.
- To change the position of warp and weft yarns as needed for the desired weave design.
- Types of sheds:
- Bottom closed shed
- Semi open shed
- Centre closed shed
- Fully open shed
- Types of shedding mechanisms:
- Crank shedding
- Tappet shedding
- Dobby shedding
- Jacquard shedding
- Jacquard shedding:
- Makes use of individual harnesses to lift individual warp yarns.
- Can be fitted to different loom types
- Positive Shedding:
- Raising and lowering of the heald frames is done using double cams
- Negative Shedding:
- Raising or lowering of heald frames is done by a mechanism that is returned by another external device, like springs.
- Crank Shedding:
- Simplest shedding mechanism
- Suitable for plain weaves
- Tappet Shedding:
- Simple, uses cams
- Inexpensive and easy to maintain
- Suitable for plain weaves
- Dobby Shedding:
- Versatile mechanism for creating a shed
- Handles 12, 16, 20, 24, 28, or 32 heald frames.
- Suitable for creating intricate weaves
- Electronic Shedding:
- Uses electromagnets to lift or lower heald frames.
- The lifting order is received electronically from computers.
- Cam:
- A specially designed rotating or sliding metal piece.
- Converts rotating motion to reciprocating motion.
- Works with a cam follower to transmit the drive.
- Dwell Period:
- The time taken by the heald frame to be stationary at a rare most position
- Directly linked to the width of the machine.
- Throw or Lift of a Cam:
- Distance by which a cam can lift a heald frame
- Repeat Size Limitations of Cams:
- Practical limit of 8-12 picks per repeat
- Related to increasing slope of cam contour and force
- Shed Settings:
- Adjusting the opening of the shed
- Increasing the length of link rods to increase shed height.
- Objectives of Shedding Motion
- To raise and lower the heald frames which carry the warp yarns.
- To make an opening for the passage of picking media.
- To change the position of warp yarns to interlace the warp & weft as per weave design.
- Various types of Tappet Shedding:
- Negative
- Positive
- Tappet Shedding - Basic Information:
- Heald frames are lowered by single cams and raised by reversing media.
- The rotary motion of the tappet cams converts to up and down motion of the heald frames.
- It gets its drive from the bottom shaft
- Shedding Motion - Additional Information:
- Shed opening and height can be adjusted.
- The shed position is related to the loom speed and picking media passage.
- Jacquard Harness:
- Suspended from the ceiling above the loom.
- Connected to the loom by a harness system of cords, heald eyes, and lingoes.
- Transmits the movement of jacquard hooks to individual warp yarns.
- Comber board is placed below the jacquard mechanism.
- Jacquard Capacity:
- Determined by the number of hooks in a row multiplied by the number of rows.
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