Self-locking

Another consequence of friction in the dynamical systems is the possibility of selflocking (or self-breaking [51]). Consider the system shown in Fig. 4.19 [7], In this model, a massless rigid rod pivoted at point 0 is contacting a rigid moving plane. 

A force R is pressing the free end of the rod against the moving plane. The normal and friction forces applied to the rod are given by N and Ff = fiN where p is the constant kinetic coefficient of friction. It can be shown that at equilibrium 

From (4.50), it is evident that if 0 tan (1/pj ), then N oo and further motion becomes impossible. In a more realistic setting where some flexibility is assumed, the motion continues by the deflection of the parts (see, e.g., Hoffmann and Gaul [98]). After sufficient deformation of the contacting bodies, slippage occurs which allows the bodies to assume their original configuration and the cycle continues. This situation is sometimes known as the sprag-slip limit cycle. 

In the example treated in the next section, a similar model is considered with the exception of the addition of vertical compliance to the pivot location (and also to the contact). 

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In 1991 a remarkable discovery was made, accidentally, with a Tp -sapphire laser pumped with an Ar+ laser. Whereas we would expect this to result in CW laser action, when a sharp jolt was given to the table supporting the laser, mode locking (Section 9.1.5) occurred. This is known as self-locking of modes, and we shall not discuss further the reasons for this and how it can be controlled. One very important property of the resulting pulses is that they are very short. Pulse widths of a few tens of femtoseconds can be produced routinely and with high pulse-to-pulse stability. Further modification to the laser can... 

Are locks, tags, and other protective materials and hardware for securing machines (e.g., chains, wedges, key blocks, adapter pins, self-locking fasteners) provided by the employer [OSHA Reference 147(c)(5)]... 

Worm, cylindrical Provide high-ratio speed reduction over wide range of speed ratios (60 1 and higher from a single reduction, can go as high as 500 1), quiet fiansmission of power between shafts at 90°, reversible unit available, low wear, can be self-locking Lower efficiency heat removal difficult, which restricts use to low-speed applications... 

PTFE has also been used in some expl nuts, where a PTFE insert provides a self-locking feature of the thread and a gas-tight seal between thread segments, bolt and housing (Ref 5). It has also been used to make inert seals or containers for pyrot compns (Ref 1)... 

Hard gelatin capsules are made self-locking by forming indentations or grooves on the inside of the... 

Balancing dampers have a self-locking regulator suitable for securing the damper at the desired setting and making adjustments. 

Special care should be exercised in systems where previous experience has indicated tray vibration problems. When tray vibration is expected, bolted-through tray connections should be used, along with lock washers or self-locking nuts, rather than frictional fastening. 

For manual tool change only the Morse taper according to ISO 296 is used (Fig. 1) on shop floors in some cases. The force and torque transfer is achieved via the frictional contact of a self-locking taper angle of 1 20. For higher loads there are models with a clamp thread or a cotter. This type of interface is used in drilling spindles and sleeves of tailstocks. 

Figure 12.7. Self-locking screws and bolts (a) nylon insert (b) nylon layer (c) adhesive film...

Figure 12.8. Locking nuts (a) standard lock nut (b) slotted and castle nuts (c) Nyloc nut(d) Aerotight nut(e) Philidas self-locking nut (f) torque lock nut...

Self-locking nuts are available which are easy to assemble and do not require a hole in the bolt or the use of a split pin. One type, known as a Nyloc nut. Fig. 12.8(c), incorporates a nylon insert round the inner top end of the nut. As the nut is screwed on, the nylon yields and forms a thread, creating high friction and resistance to loosening. 

A third type, known as a Philidas self-locking nut, Fig. 12.8(e), has a reduced diameter above the hexagon. Two slots are cut opposite each other in the reduced diameter and the metal above the slots is pushed down, which upsets the thread pitch. When screwed in position, the thread is gripped hy the upset portion, preventing the nut from working loose. 

IS.Remove the self-locking screw plug, spring, steel ball... 

Use the inner hexagon spanner to fix the ball pin remove the self-locking nut. 

Support the lower arm by jack use the inner hexagon spanner to fix the ball pin and tighten the self-locking nut to specified torque. Tightening force 63 + 5N m... 

External animal facility doors are self-closing and self locking. 

Parts shall be adequately secured so that should any wire, washer, spring, screw, nut, or similar part fall out of position or come loose, it cannot reduce the distances over the reinforced or supplementary insulation levels specified in the standards. As mentioned, parts fixed in place by screws or nuts with self-locking washers or other means are not liable to come loose, and soldered wires are not considered adequately fixed unless they are held in place near the termination independently of the soldered connection. 

C.E. Tanner, B.P. Masterson, C.E. Wieman, Atomic beam coUimation using a laser diode with a self-locking power buUdup-cavity. Opt. Lett. 13, 357 (1988)... 

The storage site should be surrounded by either a wire mesh fence of height 1.8 m or brick or concrete wall of height 2.4 m. All facilities should possess a minimum of two separate exits fitted with non-self-locking doors which open outwards. These exits should be locked when not in use. 

A self-closing, self-locking steel connector used to attach to an anchorage point. Used with a personal fall protection system. 

The replacement of self-locking devices on two secondary circuits, in parallel with the maintenance of the electric pump motors. 

P(9) AH bolts should be self-locking or otherwise fitted with locknuts. 

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