Machine Elements: Fixing, Coupling, and Sealing

Posted on Sep 9, 2024 in Technology

Machine Elements

Fixing Elements

These elements are used in the union and fixation of machine parts.

Rivet

A cylindrical body with a rounded head, made of steel, aluminum, copper, or brass. Used for permanent bonding of two or more pieces.

Pin

Unites articulated parts, allowing one piece to move by rotation.

Peg

Unites parts that are not interconnected.

Cotter

A wire shaped like a half-cylinder that is folded and has a circular head with two uneven legs. Prevents the output of pins or nuts during vibrations of the clamped parts.

Screw

A threaded cylindrical body with a head in various shapes. The main dimensions are: length of body, screw head height, distance between the hexagonal planes and edges.

  • Screw Nut: Union between parts with the help of nuts and washers (called a pass).
  • Screws Nut: The nut is replaced by a threaded hole.
  • Stud: It has two screws at the end, used when you need to assemble and disassemble screw nuts at frequent intervals.
  • Screw-Allen: Made with steel, high tensile strength. Hexagonal hole in the clamping head. Used without a nut, and their heads are embedded in a recess of the piece for a smooth finish.
  • Foundation Bolt: Barbed or serrated, made of steel or iron, used for fastening to concrete or masonry. Head is trapezoidal, thin, and harsh.
  • Self-tapping Screws: Thread stride and tapered body. They can be hot or not and sometimes have longitudinal grooves with the function of cutting the thread. Eliminates the need for a threaded hole or a nut, screw, or cut in the material being fastened.
  • For Small-Screw Assemblies: Various types of threads and heads, used in metal, wood, and plastics.

Nut

The shape of a prism or cylinder, has a threaded hole. They are hexagonal, square, or round and serve to provide tight joints between pieces.

  • Castle-Nut: Hexagonal with six radial slots that align with a hole in the screw.
  • Nut-Blind Manner: One end of the threaded hole is hidden, concealing the screw tip.
  • Nut-Butterfly Wings: Protruding thumbscrews for frequent assembly and disassembly.
  • Contaporca: Thin nut to prevent loosening and for slowing down.

Washer

A metal disc with a hole in the center. The body of the screw passes through this hole. Protects parts of the surface, avoids detachment at the contact surface, prevents loosening of the nut, removes gaps, etc.

  • Washer: Avoids damaging the surface and distributes grip underneath.
  • Pressure-Washer: Spiral coil spring to compress.
  • Washer-Starring: Provided with teeth on the internal or external diameter.

Elastic Ring

Prevents displacement of axes.

Gib

Prismatic or cylindrical, with parallel or inclined surfaces. Also moving forward.

Threads

Boss profile with a constant helical shape that develops uniformly with a cylindrical or conical surface.

  • Thread-Thin: Cars and aircraft.
  • Thread-Average: Mechanical engineering.
  • Thread-Transport or Movement: Lathes, presses, or when dismantling is constant.
Profile of the Screw
  • Triangle: The most common fasteners used in nuts.
  • Trapezoidal, Round, Square, and Sawtooth.

Coupling

Bearings

Support or guide that relies on the shaft.

  • Slide Bearings: Comprising a sleeve on a support. They are used in heavy machinery or equipment at low speed because the low speed prevents overheating. The use of plugs and lubricant reduces friction and improves the rotation axis.
    • Parts: Body of lubrication, cover, base, bushings, and shaft hole.
  • Rolling Bearings: Increased speed and less friction.
    • Bearings (used to reduce friction):
      • Radial: No axial loads and prevent displacement in the transverse axis.
      • Axial: Cannot be subjected to radial loads. Prevent displacement in the longitudinal axis.
      • Mixed: Support both types of cargo and prevent both types of displacement.
    • Application: Agricultural machinery, electric motors, shipbuilding.
    • Maintenance: Listen, look, and feel. The temperature cannot be too high, feel the vibrations.
    • Lubrication: Remove the old grease and replace it with new, or top up oil at the required level.

Gears

Organs of machines that transmit motion from one shaft to another, through teeth that successively come into contact with each other. Do not slide.

  • Cylindrical Spur Gear: Teeth parallel to each other.
  • Gear-Cylindrical Helical Teeth: Teeth cross-shaped propeller.
  • Cylindrical-Gear with Internal Teeth: The two wheels rotate in the same direction.
  • Cylindrical Gear-Rack: Sprocket mobile.
  • Conic Gear with Straight Teeth:
  • Cylindrical Gear with Slanting Teeth: Teeth angles, 8° – 20°.
  • Cylindrical Gear Teeth-V.

Belts

Maintain a link with the pulleys and transmit force and motion.

  • Flat: Conveys strength in large machines through attrition.
  • Trapezoidal: It is entirely in the form of a trapezoid.
  • Teeth: No slips.
  • Applications: Transportation of objects and car engines, air-conditioning.
  • Maintenance: Check the belt tensioning.

Steel Cables

Consists of soul and leg. The leg is composed of multiple wires around a central wire. They serve to lift, hold, fix.

  • Normal Distribution: The wires and the wires of the legs are of equal diameter.
  • Distribution Seale: The layers are alternating thick and thin wires.
  • Distribution Filler: The legs contain small diameter wires that are used as filling gaps thin.
  • Warrigton Distribution: There is at least one layer of wires of two different alternating diameters.
  • Soul Fibre: Not very heavy loads.
  • Steel Core: Very strong pull.
  • Soul of Cotton: Small cables.
  • Soul of Asbestos: Special cables, subjected to high temperatures.
  • Regular Twist or Cross: Gives stability.
  • Twist Lang or in Parallel: Abrasion resistant and flexible.
  • By Fixing Tie: Locking the loop itself.
  • Secured by Hook: Are added to the cables.
  • Housing for Sockets: Fixation and handling.
  • Lubrication: Manual, bath-dropper.
  • Problems: Reduction in diameter, corrosion, breakage of wire, birdcage (fast tension) cable crumpled soul hopped fold or knot.

Chains

A continuous loop of links that has rolls of steel and is wrapped around two sprockets (crowns). The chain transmits speed and torque between the two crowns. It is used when you cannot use belts that do not allow moisture, oil, etc.

  • Applications: Drive machines, transmissions, dirty environments, industrial pumps.
  • Roller-Chain: Most common type, the roller rotates on the tooth crown.
  • Chain Non-Rollers: They have rolls.
  • Silent-Chain: Reverse teeth to reduce noise.
  • Chain Free-Links: Used in transport, easy to remove any link.
  • Chain-Links: Links formed by round rods and soldiers. Suspension of heavy loads.
  • Chain-Slides: Several plates joined by pins, do not have rollers.
  • Chain-Blocks: Each pair of rollers with its chain, forming a block.
  • Chain-Compensated: Made of a single type of bond, with or without roll.
  • Lubrication: Manual, drip, oil bath spray.
  • Maintenance: Lubricating, reverse current, never put a new link in the middle of the old, wash it with kerosene.

Sealing Materials

Used to prevent the passage of static or dynamic liquids or gases from one medium to another. It is important that the sealant material is compatible with the product to be sealed.

  • Retainer: Is made of rubber or leather, has a profile and lip seals moving parts, has a spring to maintain tension.
  • Sealing with Gaskets: Allow settings to measure the effectiveness of the fence goes down, are manufactured in the form of rings or rope.
  • Mechanical Seal: Seal of precision using hydraulic principles to retain fluids.

Couplings

The coupling is employed when one wishes to convey a moment of rotation (rotation and force) of an axle to another machine element located coaxially with it.

  • Tight Coupling with Flanges Bolted: Suitable for transmission of high power at low speed.
  • Coupling with a Compression Sleeve or Grip: Sleeve facilitates the maintenance of machinery and equipment, with the advantage of not interfering with the placement of trees.
  • Elastomeric: Using a soft insert or type of rubber that allows a certain amount of flexibility between the coupling flanges. JAW type couplings, Perflex, elastomer shear and pre-compression are in this group.
  • Flexible Metal: Use the properties of flexible metal elements to allow movement between the coupling flanges. This group is composed of grid couplings, chain, gears and disc.