US2913908A - Starter jaw release - Google Patents

Description

United States Patent 2,913,908 STARTER JAW RELEASE Abe J. Perle, Verona, N.J., assignor to Bendix Aviation Corporation, Utica, N .Y., a corporation of Delaware Application July 1, 1957, Serial No. 669,171 j 7 Claims. (Cl. 74-7) The present invention relates to engine starters and more particularly concerns a starter having an overrunning clutch.

Turbine engines must be operated at high speeds in order to start. Turbine type starters have proved satisfactory since capable of rapidly rotating the turbine engines to high speeds. In order to avoid meshing problems between the starter jaw and the engine jaw such starters are connected to the engine and have an overrunning or one-way clutch so that starter torque is transmitted to the engine but engine torque is not transmitted to the starter gear train and turbine. Thus, upon the engine speed exceeding the starter speed, the clutch permits the engine to overrun the starter. In some instances, however, the overrunning clutch has been known to se.ze and not to permit the engine to overrun the starter. Such a malfunction can put a drag on the engine or can cause the engine to drive the starter. In either event, serious damage to either the engine or starter can result.

The primary object of the present invention is to prevent the aforenoted possibility of damage by providing improved automatic disconnect means between an engine and its starting means whereby, upon malfunctioning of the starter, a break in the drive train will result.

A further object is the provision of improved means to retract or unlatch the starter jaw when the engine torque, attempting to drive an inoperative starter, exceeds a safe value.

An additional object is to provide an improved reverse-overload release mechanism including a Belleville spring whereby a splined-mounted starter jaw is permanently moved out of engagement with an engine jaw when the engine jaw tends to urge the starter jaw out of engagement.

The accomplishment of the above objects, along with the features and advantages of the present invention, will be apparent from the following description and the accompanying drawing wherein an embodiment of the invention is illustrated by way of example.

The accompanying drawing is a side elevation in cross section of a starter embodying the invention and shows a starter jaw normally engaged with an engine jaw and re verse torque disengaging means which operates if the overrunning clutch fails.

The present invention provides improved means whereby the high speed torque output of the starter is sat isfactorily transmitted in one direction to the engine and whereby the starter will be disconnected from the engine when a small predetermined torque is applied in the reverse direction. In the disclosed embodiment, the starter jaw is held in driving connection with an engine jaw by a positioning mechanism having a Belleville spring. The starter jaw is mounted by a spline connection on a gear drive member which is coupled to starter gearing by an overrunning clutch. Upon reverse torque, the starter jaw is urged axially away from the engine jaw by the jaw teeth separating action to cause the positioning mechanism to unlatch and to permit spring means to axially Patented Nov. 24, 1959 slide the starter jaw permanently out of contact with the engine jaw.

Referring to the drawing, it is apparent that torque is transmitted from the annular gearing member 11 outwardly through the well-known one-way sprag-type clutch 13 to the clutch cover or drive plate 15 which carries the splined annular starter jaw 17. Member 11 is connected through suitable reduction gearing (not shown) to a high speed turbine (not shown). Other conventional and wellknown means having a one-way or overrunning clutch can be used to rotate'the annular portion of clutch cover 15 or a similar drive member. The cover 15 having outer and inner annular sections connected by a transverse wall is rotatably mounted by bearings 21 carried by an axial extension 23 of gear member 11. The starter jaw 17 has teeth which mesh with the teeth of engine jaw 25 which is connected by splines 27 in its axial tubular part to engine shaft 29. These mating jaws 17 and 25 are saw-toothed in circumferential profile and have the conventional axialextending and inclined faces. Mounting flange or head 31 is attached by a suitable coupling (not shown) to starter housing 33 so that the starter can be mounted on the aircraft engine. A stationary starter shaft 34 has the gear member 11 rotatably mounted thereon.

The starter jaw positioning and retracting arrangement includes an annular adjusting ring 35 threaded and locked on the splined-mounted starter jaw 17 and an annular Belleville spring retainer cuff 37 which is axially slidable on ring 35. The pair of Belleville springs 39 are mounted between an inwardly-extending lip 40 of the cufi 37 and an annular inner edge 41 of adjusting ring 35. The Belleville springs thus are inclined axially toward the starter jaw. Ring 35 also has an inwardly-extending transverse collar or lip 43 which retains an axially-extending coil spring 44 against the transverse splined part 45 of plate 15. Collar 43 is so positioned by lock ring 46. This arrangement is such that the spring 44 does not snap the Belleville springs 39 through center. Although coil spring 44 bearing against collar 43 tends to urge the splined-mounted annular jaw structure including starter jaw ring 17 and adjusting rings 35 rearwardly over the spline connection, the annular cuff 37 and Belleville springs 39 in effect constitute an opposing rigid structure, bearing against the transverse face of the plate 15, and hence prevent any axial inward movement'because the force of coil spring 44 is not suflicient to overcome the Belleville springs 39.

A heavy coil spring 51 is retained by cup 52 within starter jaw member 25 which is splined-mounted in the bore of engine shaft 29. Spring 51 is much stifier than the Belleville springs 39 and restrains the starter jaw from axial movement to the right when there are axial separat ing forces between the two slidable starter and engine jaws 17 and 25. Such axial separating forces occur when the engine attempts to drive the starter through the inclined surfaces of the mating saw-tooth jaws. It is to be noted that engine jaw arrangement is such that the engine jaw 25 cannot move to the left when the starter jaw 17 is stretched because of the rigid structure provided by bolt 55 and cup 57. Bolt 55 is axially threaded into the engine shaft 29 and cup 57 is positioned in the recess 58 in the axial tubular part of starter jaw 25.

Under conditions of normal operation, the starter cranks the engine to a specific starter cut-ofi speed. The engine then continues to accelerate to a higher normal operating speed level. clutch 13 disengages at a predetermined speed after the engine is started, the starter power train including .driving member 11 normally coasts .to rest. However, if the one-way sprag clutch 13 does not disengage orotherwise malfunctions, the engine jaw 25 drives the starter jaw 17 with the driving torque being transmitted be- Because the one-way sprag tween the angular faces of the jaw teeth rather than through the axial faces of the teeth. This sets up axial separating forces between the two slidable jaws. Engine jaw 25 is backed up by spring 51 which is a much stiffer spring than the Belleville type springs 39. Thus, the separating forces between jaws 17, 25 will result in proportionally small axial motion of the engine jaw 25 to the right and large axial motion of the starter jaw 17 to the left. Belleville springs 39 are so designed as to snap through center when the axial load caused by excessive starter drag torque reaches a dangerous level. When the Belleville type springs are snapped through center and cuff 37 slides to the right, the starter jaw 25 is rapidly retracted in an axial direction by jaw disengagement spring 44 which bears against the collar 43 and slides the starter jaw to the left over its splines. Starter jaw 17 is thus held in a position sufiiciently removed from engine jaw 25 so that re-engagement of the jaws is impossible and the engine operation can continue without transmission of any torque baclt through the malfunctioned starter.

Since the starter is unlatched or retracted sufficiently so that the starter jaw cannot engage the engine jaw, the starter cannot crank the engine when it is next desired to start up, thus signalling the fact of a starter malfunction. The starter is then removed and the source of malfunction is corrected. Finally, the starter jaw mechanism is recocked and the starter is again mounted so that the jaws are engaged for starting.

From the foregoing, it is apparent that reverse torque actuates the unlatching or retraction arrangement and permanently retracts the starter jaw so that it cannot contact the engine jaw or be driven thereby. It is to be noted that the snap action of the Belleville springs permits rapid retraction of the starter jaw so that racheting of tip part of the saw teeth of the jaws is minimized. Thus, in the event of some type of starter malfunction, after the engine has been started, means have been provided to assure continuation of engine operation without damage to the engine or additional damage to the starter and further to signal the existence of trouble to the pilot at the time he attempts operation of the starter at a later date, without effecting further damage. It is to be appreciated that transmission of torque back through the malfunctioned starter and drag on the engine is prevented by the present invention when the engine torque attempting to drive the inoperative starter exceeds a predetermined safe value.

It is to be understood that changes can be made in the disclosed embodiment of the invention by persons skilled in the art without departing from the invention as defined by the appended claims.

What is claimed is:

1. An engine starting system comprised of an engine starter having an overrunning clutch and a driving member connected to be rotated in a predetermined direction through said overrunning clutch, a driven member adapted for connection to an engine shaft and having engine jaw teeth thereon, a starter jaw member carried by said driving member and movable axially relative thereto without rotation, said starter jaw member having starter jaw teeth thereon, said teeth being so constructed as to separate when rotation is opposite to said predetermined direction, positioning means including snap action device cooperating with said driving member to position said starter teeth in engagement with said engine jaw teeth so that said teeth are normally engaged and said driven member can normally drive said driving member which is connected to said overrunning clutch, said positioning means being responsive to a predetermined reverse torque and, when so actuated, permitting said starter jaw member to be movable axially, and spring means for retracting said starter jaw teeth out of contact with said engine jaw teeth when said positioning means is actuated by said reversetor'que.

2. A reverse torque disconnect mechanism for use with an engine starter comprising a driving member, a driven member, a starter jaw member splined-connected to said driving member and movable axially relative thereto without rotation, said driven member having an engine jaw portion mating with said starter jaw member, spring means for urging said starter jaw member out of engagement, restraining means including a Belleville spring for normally positioning said starter jaw member into engagement and for normally preventing said spring means from urging said starter jaw member out of engagement, said restraining means being responsive to torque in a reverse direction exceeding a predetermined value and operative to permit said spring means to retract said starter jaw member from contact with said engine jaw portion, and said driven member having a spring arranged to oppose axial movement of said driven member away from said driving member so that the jaw member actuates said Belleville spring.

3. For use in an engine starter, the combination com prising output gearing, a drive plate, an overrunning clutch connecting said drive plate with said output gearing for transmitting torque in one direction, a starter jaw element splined-mounted to said drive plate and movable axially relative thereto without rotation, an engine jaw member adapted to mate with said starter jaw element, reverse torque means normally positioning said starter jaw element into engagement with said engine jaw member, spring means for axially biasing said starter jaw element out of engagement with said engine jaw member, and said reverse torque means axially opposing and normally preventing said spring means from disen.

gaging said starter jaw element and said engine jaw member, said reverse torque means being responsive to a predetermined reverse torque and axially operated by said starter jaw element to permit said spring means to disengage said starter jaw element from said engine jaw member.

4. An engine starter comprised of a gear train and an overrunning clutch, a starter jaw plate having an axial tubular extension and being operatively arranged to be rotated through said clutch, an annular starter jaw member splined-mounted on said extension, a sleeve slidably mounted on said starter jaw member, a Belleville spring extending between said sleeve and said starter jaw member, said sleeve and Belleville spring being arranged to oppose inward movement of said starter jaw member until a predetermined axial force is exerted on said starter jaw member when said Belleville spring snaps through center, spring means extending between said tubular extension and said starter jaw member and arranged to axially retract said starter jaw member when said Belleville spring. is snapped through center by said predetermined force.

5. In an engine starting system having an overrunning clutch drivingly connected to a transverse drive plate which has an axial extension, the improvement comprising an annular starter jaw member spline-mounted axially on said axial extension, positioning means positioning normally said starter jaw member into engagement with a mating engine jaw, spring means urging said starter jaw member inwardly, said positioning means including a snap action device which is operable by a predetermined reverse axial force, said positioning means being so constructed and arranged that said spring means can position said starter jaw member out of engagement with a mating engine jaw when said snap action device is operated whereby, when said starter jaw member is being driven, the axial force generated will operate said snap-action device and said starter jaw member will be retracted.

6. In an engine starting system having an overrunning clutch drivingly connected to a transverse drive plate which has an axial extension, the improvement comprising an annular starter jaw member spline-mounted axially on said axial extension, positioning means cooperating with the outer transverse face of said drive plate and connected to the axially-inner edge of said annular starter jaw member for normally positioning said starter jaw member into engagement with a mating engine jaw adjacent the outer edge of said axial extension, spring means urging said starter jaw member inwardly, said positioning means including a snap action device which is operable by a predetermined axially-inward force, said positioning means being so constructed and arranged that said spring means can position said starter jaw member out of engagement with a mating engine jaw adjacent the outer edge of said axial extension when said snap action device is operated whereby, when said starter jaw member is being driven, the axial force generated will operate said snap-action device and said starter jaw member will be retracted.

7. The engine starter comprised of a gear driving member connected through an overrunning clutch to a jaw plate, said jaw plate having a transverse face and an axial extension, an annular starter jaw structure mounted on said extension by means of an axial spline connection, said starter jaw structure having a starter jaw extending axially from the outer edge thereof, an engine jaw engaging said starter jaw normally, a coil spring extending axially between said starter jaw structure and said extension and urging said starter jaw structure inwardly toward said transverse face of said jaw plate, a sleeve slidably mounted on said starter jaw structure, a Belleville spring extending between said sleeve and said starter jaw structure and positioning the inner end of said sleeve in contact with said transverse face of said jaw plate, said Belleville spring being such as to prevent said coil spring from snapping said Belleville spring through center, spring means back of said engine jaw, said spring means being constructed and arranged so as to exert a greater axial resistance than said Belleville spring whereby, when an engine attempts to drive the starter, the axial force at said jaws will axially move said starter jaw and cause said Belleville spring to snap through center and said coil spring will move said starter jaw structure away from said engine jaw, said sleeve and Belleville spring being constructed so as to permit said starter jaw structure to be moved a distance such that said starter jaw and said engine jaw cannot contact each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,665,674 Metsger et a1. Jan. 12, 1954 2,721,482 Shank et a1 Oct. 25, 1955 2,728,252 Connell Dec. 27, 1955 2,752,023 Cain et a1. June 26, 1956

Images