US2845054A - Pneumatic engine starter - Google Patents

Description

y 9, 1958 R. D. PALFEYMAN ETAL 2,845,054

PNEUMATIC ENGINE STARTER Filed Sept. 15, 1954 j INV'E NTORS HE NR) TROEGER RAYMOND D. B4LFREVMAN ATTOR NEY Lam! I 2,845,054 PNEUMATHC ENGINE STARTER Raymond D. Palfreyman, (Clifton, and Henry Troeger,

Ramsey, N. .ll, assignors to Bendix Aviation tCorporatron, Teterhoro, N. L, a corporation of Delaware Application September 15, 1954, Serial No. 456,167

7 Claims. (Cl. 123-179) The present invention relates to pneumatic engine starters. It is particularly concerned with an engine starter that is powered by an air driven turbine whereby starter jaw mechanism is caused to engage and start an associated engine.

A feature of the invention is its high speed action due to its particular construction and the cooperative association of its various parts.

A further feature of the invention lies in automatic means operable to disengage the starter mechanism from the associated engine as soon as the latter is able to continue on alone.

A more particular feature of the invention lies in the construction ofthe starter jaw and the jaw advancing mechanism whereby the device is characterized by its strength, reduced size clutch plates and large starter jaw.

The invention is well adapted for the use of large diameter engine starter jaws, and it finds particular use where a large starter jaw and high jaw speeds are required, as with jet engines.

A general object of the invention is, therefore, a novel and improved pneumatic engine starter that is high speed in its operation and carries a large starter jaw.

Another object of the invention is to provide an engine starter wherein the starter jaw is advanceable axially into engagement with the jaw of an opposed engine in a practical and efficient manner.

Another object of the invention is to provide a compact pneumatic engine starter having strong, high speed jaw advancing mechanism.

A further object of the invention is to provide automatic means for restoring the mechanism of a pneumatic engine starter to normal after the completion of an engine starting operation.

The invention further lies in the particular construction of its various parts as well as in their novel arrangement and cooperative association with one another.

The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein an embodiment of the invention is illustrated. It is to be expressly understood, however, that the drawing is for purposes of illustration and description, and is not to be construed as defining the limits of the invention.

The drawing is a cross section of a pneumatic engine starter embodying the invention.

In describing the invention in detail reference is directed to the drawing, wherein there is disclosed pneumatic engine starter mechanism embodying the invention and supported in a suitable housing 1. Supported for rotation in suitable bearings 2 carried by a stationary support of the housing is an impeller wheel or turbine 3. The latter is driven by pressure air supplied through an air duct 4 and nozzles. The used air is exhausted from thehousing through suitable port means, as at 6. The supply of pressure air admitted to the turbine is controlled Patent by a remotely positioned solenoid operated air valve, not shown.

A'shaft 7 secured at one end in a hub portion 8 of the turbine projects axially into the housing. Sleeving shaft 7 is an elongated pinion 9 rotatable in end bearings 11. The pinion is clutched at its bottom end 12 with the hub of the turbine. The clutched engagement of pinion 9 and the turbine is maintained by a nut member 14 threaded on to the free end of shaft 7 and by a washer 15 intermediately of the nut member and the end wall of the plnlon.

Geared for rotation by pinion 9 are a plurality of gears 16, here three, of which two are shown. These surround pinion 9. Each is carried for rotation on suitable bearings 17 of a separate stub shaft 18 supported in stationary portions of the housing. Each gear 16 provides a right gear 19 that is in mesh with the pinion 9, and a left gear 21 that engages with an annulus gear 22 encompassing the several gears 16.

Annulus gear 22 has an axially extended hub portion 23 of reduced diameter. This reduced portion provides a hub that is suitably supported for rotation of the gear on bearings 20 that are carried by an axially extending stationary part iii of the housing. The annulus gear is connected by a slip clutch 24 with an annular short screw shaft 25 on which is engaged a travel nut 26. The latter is adapted to travel axially along shaft 25 as the latter is carried about with the rotation of the annulus gear. The travel nut serves through suitable means to advance a starter jaw member 27 axially into engagement with complementary jaws, not shown, of an associated engine.

The slip clutch 24 comprises a plurality of clutch discs 28 carried by the hub 23 of gear 22. These are interleaved'with complementary clutch discs 29 carried on the inner wall of the screw shaft 25. The right end disc of the clutch pack rests against a flat ring 31 supported by a shoulder 32 of gear 22. Resting against the end disc of the clutch pack is an annular projecting part 33 of a flat ring 34. The interleaved discs are held in clutched engagement with one another by the load of a plurality of dished washer springs 35 limited between ring 34 and a fiat nut 36 threaded upon the end portion of the hub ofgear 22. The tension of springs 35 may be regulated by adjusting the position of nut 36. V i

The screw shaft 25 serves to advance the travel nut in an axial direction. It is characterized by its heavy threads whereby it is capable of supporting a heavily loaded travel nut 26. An annular collar 30 backed by a garter spring 37 bears against the outer surface of travel nut 26. The bias provided by spring 37 and the collar is sufficient to prevent rotation of the nut as the screw shaft 25 turns. This results in the travel nutadr vancing axially along the screw shaft until limited by a shoulder or peripheral stop 38 of the screw shaft, whereupon the travel nut and screw shaft rotate together. This particular arrangement of the clutch pack relative to the screw shaft enables the use of a large jaw member 27 as is required in starting jet engines. The left interior wall ofthe travel nut is splined, the splines 39 of which engage complementary splineways of starter jaw member 27. The latter rests at its right end wall against a step 42 of a crown disc plate 43. An oil seal ring '44 is provided between the jaw member and a riser wall of the disc plate member 43. The latter seals and caps the slip clutch 24 and hub area of the annulus gear 22 as a protection against oil dripping from an opposed engine, not shown. The jaw member 27 via step 42 of plate 43 is cushioned by a wavy washer spring 45 supported by flat ring 46. The latter limits against the left end wall of thescrew shaft and limits. at its outer portion on an annular shoulder 47 of the travel nut so that spring 45 and ring 46 areadvanced with the travel nut. The jaw member is prevented from axially escaping free of the spline nut by a sealing ring or stop device 48. The latter limits against shoulders of both the travel nut and the jaw member. A snap ring 49 retained in the travel nut secures theposition of the sealing ring 48. By the foregoing structure it is evident that, as the spline nut 26 advances axially, the jaw member 27 is carried with it; that, as the travel nut limits in its axial advance and subsequently rotates, the ring 46 is spaced outward from the end of the screw shaft and the jaw member is carried about with the travel nut. Advancing of the spline nut 26 will engage the jaw member 27 with the complementary jaws of the associated engine, and rotation of the jaw member will serve to start the engine. It is apparent that wavy washer spring 45 cushions jaw member 27 during engagement with an engine jaw.

Restoration of the jaw member and travel nut occurs upon cutting off the air pressure supply to the turbine 3. When the latter action occurs, disengagement of the jaw member and restoration thereof takes place, with the aid of suitable spring means. To this end, a stub shaft 51 is bolted at one end axially to plate 43 and projects into the housing. It extends through a second disc plate 52 spaced from plate 43. Disc 52 is retained over the open end of the hub of gear 22 by a snap ring 53. A coil spring 54 about the stub shaft. is confined between an end stop thereon and the innerside of plate 52. It is clear, that as the travel nut 26 is axially advanced, the ring member 46 forces the crown disc outward. This compresses the coil spring 54. Now, when the centrifugal force acting on the screw shaft 25 decreases with the deceleration of the turbine speed, the strong coil spring 54 restores and aids in restoring the travel nut and disengaging the starter jaws. A recess 57 in the end nut of shaft 7 allows for any overthrow action of the stub shaft 51.

Automatic means operates to cut off the air pressure supply to the turbine at a time when the engine is running at a speed suflicient to carry on alone. off the air pressure permits the disengagememnt of the jaw member 27 and restoration of the travel nut 26.

This automatic restoring means includes a governor opated switch associated with one of the gears 16. To this end, the gear designated 16 is provided with an annular deep channel 58 that opens out through the left face of the gear portion 19. Fitted about the hub of the gear and resting against the inner wall of the channel is a ball retaining ring 59. The latter provides a plurality of uniformly spaced radial slots in each of which is aball 61. An annular ramp member 62 slidable on the gear hub is provided with a ramp portion that overlies the retaining ring and ball therein. The outer edge of the slidable member 62 extends beyond the outer edge of the ball retaining ring and limits against the inner wall of the channel; The ramp member is limited in the extent to which it may move leftward by a ring 63 fitted in a cylindrical wall of the channel. This ring overhangs the marginal edge of the ramp. The ramp member is normally biased to its position, overlying the balls and the retaining ring, by a dished washer or Belleville spring 64. The latter limits at its center edge against a shoulder of the ramp, and at its outer edge is limited by a second ring 65 spaced a little left of ring 63. The end wall of the slidableramp member is broad and accommodates a shoe 66 of wear resistant material affording a minimum of friction, such as nylon plastic or the like. Shoe 66 is secured to the innerside of an elongated switch contact lever 67 that is pivoted at its central area to the housing structure. The shoe end of lever 67 is normally held against the. end wall of ramp member 62 by a spring of an electric switch 71. The opposite end of lever 67 carries a screw 69 the lower end of which overlies switch 71. The screw is adjustable to provide any required buildup relative to the switch. The switch is of a conventional spring loaded type including a switch pin 72 which, when depressed,

Cutting:

opens a normally closed contact in a circuit to the solenoid controlled valve, previously mentioned. The solenoid is energized by action of the pilot of an associated craft in closing a first switch, not shown, the effect of which is to establish a circuit through the normally closed switch 71 to the solenoid. Opening of switch contact 71 de-energizes the solenoid, whereupon the solenoid valve operates to shut off the supply of pressure air to the turbine 3.

In the operation of the device, the torque of the turbine is transmitted through the gears 16 to cause the starting jaw to engage with the associated engine to start the latter. Now, as this torque transmitted to gears 16 increases, and the engine is capable of continuing on its own, the balls 61 contained in the retaining ring are driven centrifugally outward against the ramp member 62 causing the latter to advance axially against the tension of spring 64. The latter, upon being tensioned centrally outward, reaches a snapping point and then yields suddenly permitting the ramp member to snap the lever 67 clockwise to open switch 71. This opens the circuit to' the solenoid controlled air valve, causing the valve to shut off the pressure air supply to the turbine. Whereupon, the speed ofv gears 16 slackens with the deceleration of the turbine. The halls and ramp member thereupon move back to normal position under the aid of spring, and the switch 71 under the load of its' spring restores once more to closed position. Cutting off the turbine power will cause the jaw member 27 to dis engage and quickly restore under the aid of the restoring spring-54. The mechanism will not start up again until the pilot again presses the starter button.

The ball members 61 are lubricated with a suitable lubricant. This lubricant would have a tendency to centrifugally leave the balls as the latter rotates, whereupon the balls would quickly dry and score associated members. Protection against this is afforded by an overhanging bafile ring 73 which tends to block the escape" of any of the lubricant beyond the underlying spring member 64.

The arrangement of the balls in the retaining ring is of particular advantage. The halls are each loosely retained in a substantial pocket or slot of the ring, and the ring is fitted loosely to the hub of the gear member. By this arrangement as gear 16' starts to rotate, it is clear the balls will, due to inertia, roll about slightly until the speed of the gear increases. This rolling will also occur on stopping of the gear. rolling, the contacting surface of the balls relative to the associated parts is constantly changing, whereby the life of the balls and associated parts is considerably pro-- longed it is clear that the number of balls may be varied so as to change the cut-oil? speed of the governor.

While an embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. A pneumatic engine starter comprising a housing, a turbine supported in the housing, duct means for conveying a supply of pressure air to drive the turbine, a pinion gear operable by the turbine, a plurality of surrounding gears operable by the pinion gear, an annulus gear operable by the surrounding gears, a screw shaft, a slip clutch engaging the annulus gear with the screw shaft, a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut, an annular starter jaw member slidably splined to the interior surface of the travel nut, said travel nut having a ring which projects radially inwardly in front of the outer transverse end of said As a result of this screw shaft, a wavy washer spring interposed between the starter jaw member and said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of the travel nut with the screw shaft so as to eifect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, said spring being arranged to bias against axially-inward movement of said starter jaw member when said spring and jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member.

2. A pneumatic engine starter comprising a housing, a turbine supported in the housing, duct means for conveying a supply of pressure air to drive the turbine, a pinion gear operable by the turbine, a plurality of surrounding gears operable by the pinion gear, an annulus gear operable by the surrounding gears, a screw shaft, a slip clutch engaging the annulus gear with the screw shaft, a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut, an annular starter jaw member slidably splined to the interior surface of the travel nut, said.travel nut having a ring which projects radially inwardly in front of the outer transverse end of said screw shaft, a wavy washer spring interposed between the starter jaw member and said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of the travel nut with the screw shaft so as to effect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, said spring being arranged to bias against axially-inward movement of said starter jaw member when said spring and jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member, and a spring cushioned disc plate sealing over the slip clutch and providing a marginal step on which the starter jaw rests, the disc plate serving to seal over the slip clutch against oil drippings from an associated engine.

3. A pneumatic engine starter comprising a housing, a turbine supported in the housing, duct means for conveying a supply of pressure air to drive the turbine, a pinion gear operable by the turbine, a plurality of surrounding gears operable by the pinion gear, an annulus gear operable by the surrounding gears, a screw shaft, a slip clutch engaging the annulus gear with the screw shaft, a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut, an annular starter jaw member slidably splined to the interior surface of the travel nut, said travel nut having a ring which projects radially inwardly in front of the outer transverse end of said screw shaft, a wavy washer spring interposed between the starter jaw member and said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of the travel nut with the screw shaft so as to effect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, said spring being arranged to bias against axially-inward movement of said starter jaw member when said spring and jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member, one of the gears driven by said turbine having a recess therein, a plurality of ball weights and movable under centrifugal force acting on said ball weights upon rotation of said one gear, switch means operable by said ring upon movement thereof under the centrifugal force acting on said ball weights, snap spring means opposing the movement of the ring and effective upon the speed of rotation of said one gear exceeding a predetermined maximum speed to effect operation of said switch means for cutting off the supply of pressure air to drive the turbine, and spring means arranged to bias said starter jaw member so as to aid said member to return upon the cut off of a supply of pressure air.

4. A pneumatic engine starter comprising a housing, a turbine supported in the housing, duct means for conveying a supply of pressure air to drive the turbine, a pinion gear operable by the turbine, a plurality of surrounding gears operable by the pinion gear, an annulus gear operable by the surrounding gears, a screw shaft, a slip clutch engaging the annulus gear with the screw shaft, a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut, an annular starter jaw member slidably splined to the interior surface of the travel nut, said travel nut having a ring which projects radially inwardly in front of the outer transverse end of said screw shaft, a wavy washer spring interposed between the starter jaw member and said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of the travel nut with the screw shaft so as to effect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, said spring being arranged to bias against axially-inward movement of said starter jaw member when said springand jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member, one of the gears driven by said turbine having a recess therein, a plurality of ball weights, a ring in said recess carrying said ball weights and movable under centrifugal force acting on said ball weights upon rotation of said one gear, switch means operable by said ring upon movement thereof under the centrifugal force acting on said ball weights, snap spring means opposing the movement of the ring and effective upon the speed of rotation of said one gear exceeding a predetermined maximum speed to elfect operation of said switch means for cutting off the supply of pressure air to drive the turbine, a disc plate arranged to seal over the slip clutch and to provide a marginal step on which the starter jaw member rests, the disc plate serving to seal the slip clutch against oil drippings from an associated engine, and spring means arranged to bias said starter jaw member so as to aid said member to return upon a cut off of the driving power.

5. In an engine starter, a starter jaw advancing mechanism including a driving gear, a screw shaft, a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut, an annular starter jaw member slidably splined to the interior surface of the travel nut, said travel nut having a ring which projects radially inwardly in front of the outer transverse end of said screw shaft, a wavy washer spring interposed between the starter jaw member and said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of the travel nut with the screw shaft so as to etfect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, and said spring being arranged to bias against axially-inward movement of said starter jaw member when said spring and jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member.

6. In an engine starter, a starter jaw advancing mechanism including a driving gear, a screw shaft, a slip clutch engaging the driving gear with the screw shaft, a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut, an annular starter jaw member slidably splined to the interior surface of the travel nut, said travel nut having a ring which projects radially inwardly in front of the outer transverse'end of said screw shaft, a wavy washer spring interposed between the starter jaw member and said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of the travel nut with the screw shaft so as to effect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, said spring being arranged to bias against axially-inward movement of said starter jaw member when said spring and jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member, a disc plate arranged to seal over the slip clutch and to provide a marginal step ontwhich the starter jaw member rests, the disc plate serving to seal the slip clutch against oil drippings from an associated engine, and spring means to bias said starter jaw member so as to aid said member to return upon a cut off of the driving power.

7. In an engine starter, a starter jaw advancing mechanism including a driving gear, a screw shaft, a slip clutch engaging the driving gear with the screw shaft,

a travel nut axially movable along the outer surface of the screw shaft, said screw shaft having a shoulder extending outwardly for limiting the axial outward movement of said travel nut; an annular starter jaw member slidably splined to the interior surface of the travel nut, said travel nut having a ring which projects radially inwardly in front of the outer transverse end of said screw shaft, a wavy washer spring interposed between the starter jaw member and'said ring, said spring biasing said starter jaw member against a stop attached to said travel nut, means cooperating with said travel nut to oppose rotation of'the travel nut with the screw shaft so as to effect axial movement of the travel nut along the screw shaft upon rotation of the screw shaft, said spring being arranged to bias against axially-inward movement of said starter jaw member when said spring and jaw member are axially advanced with the travel nut for engagement with an engine jaw so that said spring cushions the starter jaw member, and spring means arranged to bias said starter jaw member so as to aid said member to return upon a out 01f of power to drivesaid driving gear.

References Cited in the file of this patent UNITED STATES PATENTS 2,140,083 Lansing Dec. 13, 1938 2,675,708 Orbeck Apr. 20,, 1954 2,775,894 Troeger et a1. Jan. 1, 1957

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