US2268243A - Ratchet and pawl mechanism - Google Patents

Description

Patented Dec. 30, 1941 2,268,243 I RATCHET AND PAWL MECHANISM John C. Curtis, Claremont, N. H., assignor to` Sullivan Machinery Company, a, corporation of' Massachusetts Application August 2, 1940, serial No. 349,507

ZIClaims. (Cl. 'I4-,577) y This invention relates` `to ratchet and pawl mechanisms and more particularly to ratchet and `pawl mechanisms of thetype adapted especially for use in hammerlrock drills. v A

It is an-object'of this invention to provide an improved ratchet and pawl mechanism. Another `object is to provide in a ratchet and `pawl mechanism of the type adapted for use in hammer rock drills, improved meansfor locking the pawls against inadvertent release with respect to the `pawl carrier. Still another object isto provide an improved ratchet and pawl mechanism in which the pawls are locked against inadvertent release from the lpawl carrier irrespective of their supported position but may be released when desired. It is still ,another object to provide a ratchet and pawl mechanism having improved means for con- "tinuously urging the pawlsintoengagement with the ratchet and `for locking the pawls against inadvertent release from the pawl carrier. Another object is to provide inaratchet and pawl mechanism an improved spring pressed plunger engaging a pawl at points cl'osely adjacent to the axis of the plunger for urging the pawl into engagement with the ratchet, said plunger having formed thereon meansA for locking the pawl against inadvertent release from the pawl carrier. Still another object is to provide an improved spring pressed plunger for a ratchet and pawl mechanism movable to different positions for presenting diierent portions to the pawl for wear.

Other objects and` advantages of the invention will, however, hereinafter more fully appear.

Inthe accompanying drawing there are shown for` purposes of illustration two forms which the invention may assume in practice.

In this drawing:. I

Fig. l is a view mainly in longitudinal vertical section, but with parts in elevation, showing `a hammer rock drill in which an illustrative embodiment of the invention is incorporated.

Fig.` is a side elevational View of one of the pawls.

Fig.` 6` is a perspective view of the pawl shown in Fig. 5.

Fig. 7 is a side elevational view of one of the 'spring pressed plungers.

Fig. `8 is a View taken on the plane of the line 8-8 of Fig. 7. l

Fig. 9 is a side elevational view of the plunger shown in Fig. '7 turned through 90".l

Fig.v 10 is a side elevational View of a modied I form` of spring pressed plunger.

In this illustrative embodiment of the invention there is shown a `hammer type rock drill, generally designated I, having a cylinder 2 that isvprovided with a bore 3 within which a piston 4 is reciprocably contained. Formed on the forward end of the piston is an elongated striking bar 5 of reduced cross section that is reciprocably guided in a bushing 1 mounted in a front cyl- I inder head 8 for delivering impact blows to the shank of a drill steel. Formed in the striking bar are straight grooves 9 slidingly interlocked with straight keys I0 on a chuck member I| for transmitting rotary motion of the piston to the drill Steel in the usual manner. Reciprocations mounted for rotation within a rear cylinder head I1 and a rear head block I8. Formed integrally with `the rifle bar I6 adjacent its rear end is a pawl carrier I9 which carries two pairs of pawls ,2I, 2| and 22, `22. The pawlsare symmetrical in end elevation and in outline in side elevation and r cooperate with teeth `23 of a ratchet ring 24 which is threaded within the rear` head block I8. The pawls 2| and 22 `are suitably pivotally supported in sockets 26 and 2l respectively in the pawl carrier I9, these `sockets being generally cylindrical I and opening into spaces 28 formed bythe cutting away of the periphery of the pawl carrier. The spaces 28 are so formed as to permit` the. pawls to swing outwardly a suiicient `distance to `engage fully the ratchet teeth 23, but to restrain them from excessive outward movement.` To maintain the pawls in yieldingengagement withthe ratchet teeth 23, pawl-engaging plungers 30 are provided, these plungers being disposed in bores 3| extending chordally of the pawl carrier and being pressed yieldingly against the inner surfaces of the pawls by springs 32. Two of the bores, 3Ia, 3Ia, are herein arranged to the rear of the median transverse plane of the pawl carrier; the other two, 3| b, 3| b, are arranged forwardly of that plane. The bores 3|a, 3Ia are parallel to each other, as are the bores 31D, 3|b; and the bores 31a, 31a are perpendicular to lines parallel to the bores Sib, 3Ib.

Each of the pawls comprises a blade portion r34 engageable with the teeth 23 of the ratchet and a pivot portion 35 pivotally seated in one of the sockets 26 and 21. An opening 31 extends completely through the blade portion of each pawl at a point shown herein as positioned between the center and one end of the pawl and close to the pivot portion 35. Since the pawls are symmetrical in shape they may be released from their sockets and turned end for "e'nd and be reinserted within other Ysoclr'ets to present other portions of the pawls ifor 4engagement vwith the ratchet teeth after the iirst pawl engaging portion becomes worn.

In order toimpart to each pawl a substantially constant pressure throughout its full swing for urging it into engagement With the ratchet teeth, and in order to obtain contact between 1 the plunger and the pawl at pointswhich would prevent `a binding of theplunger in its bore and which would increasethe effective swinging force of the pawl, the plunger is cut away adjacent the pivottportion 35 of theipawl as a't 38k to provide shoulders 39 on the plunger for engaging the blade of the pawl. VThe plunger is cut back at 38 a suflicient distance to prevent engagement of the plunger with the pawl, even when the plunger moves outwardly to force the pawl into full engagement with a ratchet tooth, at points lbetween the engagement of the shoulders 39 with the pawl and the inner end of the VpawL Ihe arrangement of the pawl and its plunger is such that when the pawl rides over 'the points of the ratchet teeth, the side of the pawl blade next to the plunger is at such an angle that therel is only an engagement between the plunger and `the 'pawl at the shoulders 39 alongthe edgewhere theplunger is cut back. Formed on each plunger atits end engaging the pawl is a reduced axial "projection 40 extending within an opening 3l in a pawl :for positively locking vthe pawl in Iposition on the' pawl carrier. In order that the 'plungers may be inserted into or removed from within their bores when the pawls are removed from the pawl carrier, there `are provided grooves 4| in the pawl carrier in alinement with the inner walls of the plunger bores. Y,

A modied form of plunger 43 is shown'inFig. 10, and is likethe plunger 30 except that it is cut away at opposite sides, as at 44 `and'l5,V to provide shoulders 46 providing two edges '41 and d8.` When one of the edges'becomes worn down the plunger maybe rotatedthrough 180 to bring theother edge into position for engaging a pawl.v

'From the foregoingdescription, it Ywill be noted thatthere is provided Van improved ratchet and pawljmechanism in which the effective force of the spring-pressed plungers for urging 'the pawls 'intoengagement with the ratchet teeth is maintained uniform and is applied at Ypoints lying close toa plane including the axis of the plunger. It will further be noted that thereis provided rneans for locking the pawls against accidental .removal while permitting swinging movement of the pawls about their `pivot axes on the pawl carrier. It will also be noted that the pawls are reversible to provide different portions which are subjected to wear for engaging the ratchet teeth, and that spring-pressed plungers are provided each having a plurality of pawl engaging portions selectively engageable with a pawl to distribute the wear. The structure is simple, of rugged construction, andjwell adapted for its intended purpose.

While there are in this application specifically described two forms which the invention may assume in practice, it will be understood that these `forms vof the same are shown for purposes of 'illustration'l and that the invention may be modi'ed `and embodied in various other forms without departing Afrom its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is: Y

1. In a ratchet and pawl mechanism, in cornbination, relatively rotatable ratchet and pawl carrier elements. pawls pivotally mounted on said pawl carrier element and engageable with the teeth of said ratchet element, said pawls having generally cylindrical pivot portions and projecting blade portions, said blade portions engaging Y ...points lying in the case of each plunger and the pawl with which it is associated in a plane eX- tending transversely-of said pawl and in close parallelism with the axis of said plunger.

` 2. In a ratchet landpawl mechanism, in combination, relatively rotatable ratchet and pawl carrier elements, pawls pivotally mounted on said pawl carrier element and engageable with the` teeth of said ratchet element, and plungers mounted on said pawl carrier element and respectively yieldingly pressed into engagement with said.{pawls between the ends of the latter for .yieldingly urging said pawls 4into engagement with the ratchetteeth, said plungers having reduced locking projections extending lengthwiseof the axes of said plungers and said pawls hav- `ing openings extending therethrough and within which saidlocking projections project, the pivotal mountings for saidrpawls being so arranged that the faces of said pawls4 adjacent their associated plungers are spaced' over 90. from the axes of saidplungers in all positions of the pawls While engaging the ratchet-teeth, and said plungers being cut away for limiting contact between each plunger and the associated pawl, during engagement ofthe latter 'with the ratchet teeth, Y 1

topoints lying ,in a planeextending transversely of "said pawl and in vclose parallelism with the axis of said plunger. Y

JOHN C. CURTIS.

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