Section 80.—SPRINGS.

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1454. Double angular slide valvefor varying the cut off by a transverse motion given to the valve from outside, either by hand gear or by the governor, the valve being made wider than the valve face, as dotted lines.

1455. H. Jack’s variable expansion gear,with one eccentric. Patent No. 4167/85.

1456. Variable cut-off valveon the back of the main slide, the rod of which can be revolved by hand or from the governor to vary the opening of the cut off valves.

1457. A plan to effect the same objectbut by a cylindrical cut off valve.

1458. English’s expansion gear.Two eccentrics. The expansion valve has no lap, and the gear gives a constant relative motion to both valves.

1459. Tappet gear,sometimes used for water-pressure engines, &c.

1460. Open spiral springfor tension.

1461. Close spiral spring.

1462. Open spiral springfor compression.

1463. Open spiral spring(square thread) for compression.

1464. Double volute chair spring.

1465. Spindle-shaped open or close spiral springfor tension.

1466. Parallel open or close spiral springwith coned ends.

1467&1468. Volute springs.

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1469. Torsional spiral spring.

1470. Wire staple torsional spiral spring,used for hinging; the ends of the wire are bent at a right angle and driven into the wood.

1471. Fixed spring.

1472&1473. Sear springs.

1474. Flat spiral spring.

1475. Plate spring.

1476. Indiarubber springfor tension.

1477. Wire spring.

1478. Ribbon springfor torsion.

1479. Compound rubber disc spring.

1480. Air cushion or spring piston.

1481. Laminated plate wagon spring.

1482. Compound dished disc or bent plate spring.

1483. Loop spring.

1484. Flat spiral spring, clock spring or coil spring.

1485. Split ring spring.

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1486. Spring polefor foot hammer motion, &c.

1487to1489. Spring washers.

1490. Spindle-shaped compression spring.

1491. Flat spiral springfor piston rings.

See alsoNos. 1729,630,1501,1503,11,767,768; andSection 35(Elastic Wheels) for other forms of springs and applications of them.

For equalising the tension of a spring, seeNo. 1592and1602.

1492. Cam gear;operates by gripping the wood guides by a serrated eccentric cam surface on the breakage of the rope, the cam being pulled round by a spring which is kept out of action by the tension of the rope until it breaks.

1493. Strut or pawl gear;explains itself.

1494. Double wedge gear.

1495. Governor gear.The rope attached to the cage drives a governor acting on a brake or catch which is thrown into action if the cage gains excessive speed, used in Attwood Beaver’s Patent; American Elevator Co., &c.

1496. Rack and pawl gear.

1497. Cross grip lever gear.

1498. Safety hookto prevent accident from overwinding; the projecting hornsA Astrike the edges of the plateB, and throw the shackleCat top out of gear.

For hoist doorsthe best appliance is an ordinary spring lock opened only by a key, the doors being provided with springs to close them. Various automatic doors, revolving shutters, and other devices have also been tried. A simple and effectual protection is a continuous open-work screen wound upon a roller at top and bottom of lift, and attached to the top and bottom of cage and rising and falling with it, so that the doors into lift are all covered at all times except the one at which the cage happens to stand.

Safety valves(seeSection 89). Various automatic alarm signals are applied to boilers to warn against low water or excessive pressure.

Automatic valvesand other devices are applied to pumping and steam engines to prevent running away. SeenotetoSection 41.

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To collect and discharge condensed steam from pipes, &c.

1499. Trap operated by a modified form of ball cock,which rises as the box fills with condensed water and opens the discharge valve.

1500. Effects the same object by a floating basin.The condensed water enters the box outside the basin, fills it, and lifts the basin which closes the discharge outlet; when the box is full the water overflows into the basin and sinks it, thus opening the outlet valve.

1501. Trap operated by expansionof a bent spring which closes the valve, on the principle that live steam is hotter than the water condensed from it.

1502. Tredgold’s trap.The valve is opened by a simple float.

1503. Wilson’s trap,like1501, is dependent on the different expansion of a spring under the difference of temperature of the steam and condensed water. In this case the spring is formed of a steel and brass plate riveted together.

There are many other forms upon similar principles to the foregoing.

The valves used for starting steam and other engines are usually merely of the ordinary screw down or sliding types. SeeSection 89.

For starting and controlling all other forms of reciprocating cylinder motors, such as hydraulic lifting cylinders and presses for all purposes, the ordinary slide valve with either two or three ports is the common device; also the ordinary three or four way cock. SeeSection 89.

1504. Locke’s 3-way balanced valve,which is balanced in all positions.Ais the supply,Bthe cylinder branch, andCexhaust.

1505. Fenby’s 3-way equilibrium starting valve.Asupply,Bcylinder branch,Cexhaust.

1506. Auxiliary valve and pistonsto start large slide valves too heavy for direct hand power. A 3-way cock is shown as the auxiliary valve, but a small slide valve or piston valve may be substituted. Seenoteat foot ofSection 93, alsoNos. 1740and1741.

1507. Auxiliary valve and bellowsfor air, as sometimes used in large organs to open heavy “pallets.” The small valveAis opened by the pressure of the finger on the corresponding key of keyboard, and allows the pressure of air to enter the small bellows which operates the large valveB.

1508. Four plunger valve,used for double power hydraulic lift cylinders employing a trunk piston. For the low power the pressure water acts on both sides of the piston; for the double power it acts only on the back of piston, the front side being then open to the exhaust.

1509. A starting valve,having two ordinary wing or spindle valves, either of which is lifted by a double cam or wiper on a spindle passing through a stuffing box on side of valve case.Asupply,Bcylinder port,Cexhaust.

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1510&1511. Two methods of operating starting valvesfor hydraulic lifting machines. 1510 acts by counter balance weights and a single rope, each of the weights being heavy enough to move the valve, and 1511 by an endless rope.

1512. Low pressure starting valve,used for piston hydraulic cylinders in which the lifting is performed by the down stroke of the piston rod, and in lowering, the valve allows the water to pass from above to below the piston, the water being exhausted from below the piston on its down stroke when the valve is in the position shown.

1513. Oscillating valve,with plunger face kept up by a spring. The oscillating valve has two ports passing out at opposite ends, through stuffing boxes, to either end of the cylinder; the inlet is at top and discharge at bottom.

1514. Balanced self-acting starting valve,suitable for large machines and low pressure. The upper piston is larger than the lower or main piston, and the space above the upper piston can be put in communication with the pressure water below it, or the exhaust port by the small piston valve at top operated by the hand gear; so that the main piston is operated by the pressure water acting on it.

1515. Spur gearing.For construction of teeth see text books.

1516. Strongest form of spur teethfor motion in one direction only.

1517. Half shrouded spur teeth.

1518. Whole shrouded spur teeth.

1519. Double helical spur teeth,stronger by 15 per cent. than straight teeth; work without backlash or noise, and may be half or whole shrouded; section of tooth on plane of motion is the same as the ordinary spur teeth (No. 1515).

1520. Crown wheel and pinion.

1521. Long teeth spur wheels or “star” wheels.Used on roller mangles, &c., where the centres rise and fall.

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1522. Plain bevil gear;shafts at right angles.

1523. Plain bevil gear;shafts at acute angles.

1524. Plain bevil gear;shafts at obtuse angle.

1525. Plain bevil gear;four shafts at right angles.

1526. Skew bevils;shafts not in line with one another.

Note.—Where the pair are both of same diameter they are called “mitre wheels.”

1527. Spur wheel and pinion;to increase or decrease power and speed the diameters can be varied to almost any proportion.

1528. “Screw gear”;single helical gear.

1529. Skew spur wheels;shafts not parallel.

1530. Dr. Hooke’s gear.Three or more separate wheels of similar or dissimilar pitch fixed together so as to divide the pitch and reduce backlash.

1531. The same result obtained by two wheels,one fixed to shaft, the other loose and forced round by a spring so as to follow the pitch of the pinion and destroy all backlash.

1532. Mortise wheel teeth.

1533. Mortise wheel teeth;another method.

Note.—Wood teeth are usually one-third thicker than the iron teeth they gear into.

1534. Pin wheel and pinion gear.

1535. Lantern wheel.

1536. Screw gear,used in place of bevil gear. Shafts at right angles; teeth at an angle of 45°.

1537. Variable speed cone gear.

1538. Variable speed square gear.

1539. Variable speed oval or elliptical gear.

1540. Irregular gear.

1541. Internal or epicycloidal gear.SeeNos. 550and1545.

Used for differential blocks, &c. Note that both wheel and pinion run in the same direction, and that more teeth are in gear at one time than with external gear asNo. 1527.

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1542&1543. Varieties of “mangle” gear.The pinion being revolved continuously in one direction produces a reciprocating motion of the wheel; the pinion shaft travels from inside the wheel to outside, andvice versâ, by rising and falling in the slot in the frame. See alsoNo. 423.

1544. Differential gear.SeeSection 31. One wheel has one or more teeth more than the other; used for counters, &c.

1545. Moore’s patent differential epicycloidal gear.The pinion and wheel are loose on the shaft and eccentric. One wheel has one tooth more than the other.

1546. Multiplying bevil gear.Ais a fixed wheel, the crossCis keyed to shaft,Bloose on ditto,DandEloose onC; thenBis driven at a speed greater than the shaft in proportion to the diameters of the gear. See Patent No. 12,696, 1884.

1547. Double worm gear,right and left hand threads. Neutralises the end thrust on shaft.AandBmay be geared together.

1548. Pointed gear;used for light work and for minimum of friction.

1549. Curved worm gear,for heavy strains. Several teeth are in gear at once, but the thread, having a varying section and pitch, is difficult to cut.

1550. Antifriction worm gear(Hawkins’). The wheel has four rollers; when one pair is nearly out of gear with the worm, the next pair is coming into gear. This worm is also difficult to cut.

1551. Crown worm gear.

1552. Ball joint mitre gear.

1553. Multiplying rack gear.The upper moving rack is driven at twice the speed of the spur wheel rod. The lower rack is fixed; used on planing and printing machines.

1554to1557. Varieties of worm gear,with straight, hollowed, and curved teeth; the latter are strongest.

1558. Worm and rack gear.

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1559. Differential worm gear.The worm gears into two wheels, one having one tooth more than the other.