Overview:
The book, written by Thomas Roberts in 1912, offers a comprehensive guide to tappet and dobby looms, a crucial part of the textile industry at the time. The text starts by classifying looms, including tappet, dobby, and jacquard looms, highlighting the types of fabrics they produce. It then delves into the installation and arrangement of looms, emphasizing efficient utilization of space and light for optimal productivity.
The book meticulously explains the various motions involved in weaving, including primary motions like shedding, picking, and beating-up, alongside secondary motions like letting-off and setting-up, and auxiliary motions like the weft stop motion. Detailed descriptions of the mechanism and management of each motion are provided, focusing on the importance of proper timing and alignment for achieving optimal efficiency and preventing defects in the fabric.
Key Findings:
- Loom driving mechanisms: This text highlights the importance of choosing the right driving mechanism (loose and fast pulleys or friction drive) for different loom types and fabric weights.
- Eccentric driving: While eccentric driving wheels can potentially improve performance for heavy wefts, they come with the risk of increased strain and breakages on the loom, especially in high-speed applications.
- Timing of motions: The timing of the shedding, picking, and box motions is crucial for efficient weaving. The author emphasizes the need for careful adjustment to optimize these motions for different fabrics and designs.
- Importance of proper maintenance: The text stresses the need for skilled tuners to maintain looms and ensure optimal performance. Proper preparation of warp and weft yarns is also essential for smooth operation and increased production.
Learning:
- Understanding Loom Mechanism: Readers will learn the inner workings of tappet and dobby looms, gaining a deeper understanding of the various motions involved in weaving.
- Impact of Motion Timing: The text highlights how the timing of various motions within the loom significantly impacts the quality and efficiency of the weaving process.
- Factors Affecting Loom Efficiency: Readers will learn about the various factors that influence loom efficiency, including driving mechanisms, loom maintenance, and the preparation of yarns.
- Fabric Defects and their Causes: The text outlines common fabric defects related to weaving and provides insights into their root causes, such as improper shedding, picking, or box motions.
Historical Context:
This text was written in 1912, a period of significant industrial growth and technological advancement. The book reflects the evolving practices of the weaving industry at that time, including the increasing use of power looms and the ongoing search for greater efficiency and productivity.
Facts:
- Loom Types: There are three main types of looms: tappet, dobby, and jacquard looms, each specialized for different weave complexities and fabric types.
- Right and Left Hand Looms: Looms are designed as right and left-hand versions for efficient space utilization and power transmission.
- Open and Crossed Belts: Looms driven by crossed belts tend to run up to speed more efficiently than those driven by open belts.
- Importance of Clean Belts: Belts should be kept clean to maintain proper friction and prevent slippage.
- Purpose of the Brake: The brake prevents the loom from over-running when thrown off, typically by a weft stop motion or warp protector.
- Types of Brake Motions: Different brake motions are used for different loom types and purposes, such as stopping the loom on weft failure or minimizing vibrations during knock-offs.
- Balance Wheel Function: The balance wheel assists in overcoming variable resistance during crankshaft rotation, providing a slight boost to the loom’s momentum.
- Friction Driving Advantages: Friction driving offers immediate power transmission, reducing knock-offs and providing a more effective drive than loose and fast pulley systems.
- Indirect Driving for Heavy Wefts: Indirect driving motion, often using bevel and spur gears, is sometimes favored for looms weaving heavy wefted goods.
- Speed Calculation Formula: The formula D R = d r can be used to calculate the speed of shafts, drum size, and change wheels required for different loom configurations.
- Principles of Motion: Loom mechanisms use various principles like spur and bevel gear gearing, worm and worm-wheel gearing, ratchet wheel and pawl, and levers to achieve complex motions.
- Importance of the Going Part: The going part (or lay) of the loom plays a crucial role in beating-up the weft and providing a smooth path for the shuttle.
- Types of Going Part Construction: Different loom types utilize various designs for the going part to ensure strength and stability, including single-piece construction, angle plates, and double battens.
- Importance of a True Race: The race on top of the lay is crucial for the shuttle’s smooth movement. Defects in the race can lead to shuttle flying out or warp threads being cut.
- Variable Movement of the Going Part: The going part exhibits a variable movement due to the crank’s rotation and the connecting arm’s position.
- Eccentricity of the Going Part: The eccentricity of the going part is determined by the crank size, connector arm length, and crankshaft position, influencing the dwell time for shuttle passage.
- Position of the Reed: The position of the reed at the beat-up is critical for ensuring a square blow to the weft and minimizing vibrations.
- Warp Resistance in Different Weaves: The resistance offered by the warp to the beat-up can vary depending on the weave design and the shedding motion used.
- Early Shedding for Heavy Wefts: Early shedding, where the shed is formed before the shuttle reaches the beat-up, can be beneficial for weaving heavy wefted goods.
- Tappet Construction and Motion: The construction of tappets determines the timing of the shed and the nature of motion imparted to the healds.
Statistics:
- Tappet Loom Range: Tappet looms typically accommodate between 2 and 12 heald shafts, depending on the type of weave.
- Dobby Loom Capacity: Dobby looms can accommodate up to 48 heald shafts, but 16, 24, and 36-shaft dobbies are more common.
- Sectional Tappet Limitations: Sectional tappets are typically limited to weaving fabrics with weaves complete on not more than six picks in a repeat.
- Barrel Tappet Flexibility: Barrel tappets are more flexible, allowing for the production of weaves on two, three, four, six, and eight picks.
- Bradford Tappet Capacity: Bradford tappet looms are often fitted with 13 heald shafts for more complex weaves.
- Change Wheel Calculation Example: A 7-pick pattern on a Bradford tappet loom with a 120-tooth tappet wheel requires intermediate wheels with 42 and 30 teeth.
- Treadle Pulley Stroke: In Bradford tappet looms, the stroke of the treadle pulley can be adjusted to achieve the desired shed depth.
- Shuttle Depth Allowance: A 13/4-inch deep shuttle can be used with a 2-inch deep shed, allowing for 1/4-inch clearance between the shuttle and the top shed line.
- Warp Protector Stop Motion Timing: The warp protector stop motion typically operates within a short timeframe, typically a few degrees of crankshaft rotation.
- Box Motion Timing: Box motions are timed to ensure that the boxes are fully changed before the shuttle is picked.
- Letting-off and Setting-up Motions: The timing of these motions varies depending on whether they are negative or positive.
- Maximum Dwell Time for Healds: In some looms, the minimum dwell time for healds is calculated as 1/4 of a crankshaft revolution.
- Tappet Construction Circles: The outline of a tappet is constructed using four circles representing the inner circle, outer circle, and the two construction circles for the treadle pulley.
- Tappet Outline Divisions: Each section of the tappet outline represents one pick of the weave and one complete revolution of the crankshaft.
- Heald Pulley Limitations: Heald pulleys are limited to weaves where the movements of the threads are reversals, typically used for weaves with an even number of threads.
- Stocks and Bowls Capacity: Stocks and bowls can be employed for weaves with an odd number of shafts, as long as the same number of shafts are lifted and depressed on each pick.
- Kenyon’s Under-Motion Flexibility: Kenyon’s under-motion is highly flexible, accommodating any weave regardless of interlacing order or the number of shafts lifted and depressed.
Terms:
- Tappet Loom: A loom that uses tappets to control the heald shafts, resulting in simpler weaves.
- Dobby Loom: A loom that uses dobby mechanism for more complex weaves.
- Jacquard Loom: A loom with a jacquard machine, enabling intricate and elaborate fabric patterns.
- Shedding Motion: The motion that controls the heald shafts to create the shed for shuttle passage.
- Picking Motion: The motion that drives the shuttle across the race.
- Beating-up Motion: The motion that pushes the weft into place, controlled by the going part (lay) of the loom.
- Letting-off Motion: The motion that regulates the warp tension as the fabric is woven.
- Setting-up Motion: The motion that controls the take-up of woven fabric on the cloth beam.
- Going Part: The lay of the loom responsible for beating-up the weft and guiding the shuttle.
- Race: A smooth surface on top of the lay, usually made of wood or steel, that the shuttle travels across.
Examples:
- 2×2 Twill Example: The text uses the 2×2 twill weave to illustrate the operation of the sectional tappet, explaining how the tappets are arranged and connected to the heald shafts.
- Bradford Tappet Construction: The text explains the construction and operation of the Bradford tappet, detailing how the tappets, treadles, levers, and heald shafts work together to form the shed.
- Change Wheel Calculation: The example of a 7-pick pattern on a Bradford tappet loom demonstrates how to calculate the number of teeth needed in the change wheels to achieve the desired speed.
- Tappet Outline Drawing: The text provides step-by-step instructions on how to draw the outline of a tappet for a specific weave, illustrating the process of designing the tappet’s contour.
- Heald Pulley Application: The example of 2-and-2 twill shows how heald pulleys can be used to reverse the movement of two heald shafts that have reciprocal interlacings.
- Stocks and Bowls Operation: The text illustrates how stocks and bowls with stepped pulleys work together to compensate for slackening and tightening of heald cords during shed formation.
- Kenyon’s Under-Motion: The text explains the workings of Kenyon’s under-motion, highlighting how the spring, tumblers, and levers are used to reverse the action of the tappet on each heald shaft.
- Heavy Wefted Goods: The text cites the example of weaving heavy wefted goods to illustrate why early shedding can be advantageous, as it allows the weft to be inserted more effectively into the shed.
- Clearing the Shed for Coarse Yarns: The text describes the challenge of weaving with coarse, cross-bred worsted or low cheviot woollen yarns, which tend to have loose fibers that can obstruct shed formation, and outlines various strategies to overcome this issue, including early shedding.
- Troughing the Shed: The text mentions the principle of troughing the shed, which is used to prevent reed marks and improve fabric cover, typically in combination with early shedding.
Conclusion:
This 1912 guide to tappet and dobby looms provides a wealth of information for anyone seeking a detailed understanding of these essential weaving mechanisms. The text goes beyond simple descriptions, delving into the intricacies of each motion and the factors that influence loom efficiency and fabric quality. Understanding the importance of proper timing, maintenance, and the selection of appropriate driving mechanisms is critical for achieving optimal performance and reducing fabric defects. While the technology has advanced significantly since 1912, the principles outlined in this text remain fundamental to modern weaving practices.