US2473566A - Self-reversing power jack - Google Patents

Description

June 21, 1949. BRASSELL 2,473,566

SELF-REVERSING POWER JACK Filed April 4, 1946 3 Sheets-Sheet l INVENTOR. BRYAN BRAS- s 5;}, L

ATTORNEYS June 21, 1949. s. BRASSELL SELF-REVERSING POWER JACK 3 Sheets-Sheet 2 Filed April 4, 1946 L Y ai 0W n T E MS m ms r w A m B N A y W a B i w A m t .1. l /J wv Y/l w u. a .m 2 a A v- Patented June 21, 1949 UNITED STATES PATENT OFFICE 18 Claims.

This invention relates to power transmitting apparatus and mechanical movements, and more particularly to motion converting mechanism.

One of the objects of my invention is the provision of reliable and highly satisfactory motion converting mechanism which eiliciently and readily effects the conversion of rotary motion to linear motion.

Another object is the provision of power transmitting mechanism whereby unidirectional rotation from a source of motion is readily and effectlvely transformed into linear or reciprocatory action.

A further object is to provide mechanism of the character referred to which is simple to install, and which is well calculated to serve under many different conditions of actual practical use.

Another object of my invention is the provision of power transmitting apparatus, as for example a power transmitting system, including and utilizing motion converting mechanism of the character noted.

A still further object is the provision of rotary to linear motion mechanism capable of simultaneously developing multiple rotations contributing to the achievement of quick strokes of linear movement.

A further object is to provide efficient and practical mechanism for automatically converting rotary motion to reversing strokes or reciprocation, all with minimum stress on working parts during reversal of any given stroke.

Otherobjects in part will be obvious and in part pointed out hereinafter.

My invention therefore consists in the combination of elements, features of construction and arrangement of parts, as described herein, the scope of the application of which is indicated in the following claims.

In the accompanying drawing illustrating certain features of my invention:

Fig. 1 depicts an embodiment of the rotary to linear or reciprocatory motion converting mechanism in sectional elevation;

Fig. 2 represents, in elevation, the same apparatus as in Fig. 1;

Fig. 3 is a horizontal section of the mechanism taken substantially on the line 33 in Fig. 2;

Fig. 4 is a fragmentary view of certain rotative and reciprocativ elements represented in Fig. 1;

Fig. 5 presents in detail a form of joint for transmitting rotation and reciprocation;

Fig. 6 depicts, in elevational view, a modified form of stroke selector means of the conversion mechanism;

Fig. 7 is a sectional elevation corresponding to Fig. 6;

Fig. 8 is a fragmentary view of certain detent mechanism of the modified stroke selector means;

Fig. 9 is a view, in elevation, representing modified unidirectional rotary motion transmitting means of the rotary to linear or reciprocatory motion converting mechanism;

Fig. 10 is a fragmentary sectional elevation of certain elements represented in Fig. 9; and

Fig. 11 schematically represents a power transmitting system including a rotary to reciprocatory motion converting mechanism.

Similar reference characters designate corresponding parts throughout the figures.

As conducive to a clearer understanding of certain features of my invention, it may be noted at this point that mechanisms for converting rotary motion to linear motion have come into widespread demand for such purposes as in the pumping of fluids, in tooling and machining operations, for the steering of craft, in operating power presses and hoists, and. for a great variety of other uses including those in which a linear mechanical movement as derived from rotary motion is depended upon to set related equipment or transmit linear impulses to the same. While there are quite some few rotary to linear motion mechanisms in the prior art, many of these are open to such objections as being difficult of control during use, particularly as regards the achievement of satisfactory and reliable reversal of strokes or continuation of an arrested stroke, for making up the linear movement. Then too, certain of the prior art mechanisms are not readily adaptable to receive unidirectional rotary motion from a suitable source of power and convert the same to linear motion. Still other heretofore known motion converting mechanisms lack efiiciency and positiveness of mechanical action. In other instances mechanisms are so mechanically complicated and space consuming as to render installation inadvisable.

An outstanding object of my invention accordingly is the provision of a simple, compact and reliable motion converting mechanism wherein a transition from unidirectional rotary motion to reciprocatory motion is positively and efiiciently achieved under highly satisfactory conditions of reversing or alternating the stroke of reciprocation.

Referring now more particularly to the practice of my invention, attention is invited to Figs. 1 and 2 of the drawings wherein there is represented a motion converting mechanism, generally indi- 3 cated by the numeral ID. This illustrative mechanism of my invention includes a suitable casing l I, through which there extends a drive shaft l2, the latter being journalled as in bearings i la, I lb, and illustratively forming an included part of selectively operative means for transmitting unidirectional rotation to either of oppositely disposed co-axial gears 2| and 23 of epicyclic or differential gearing. Two gears, 14 and I5, and an intermediatelypositioned sleeve I6 are mounted on the shaft. Thegears' just mentioned are capable of idling, and of becoming driving gears when engaged into service by selective movement of sleeve it which is splined to the drive shaft'in' such fashion as to be free for longitudinal movement to locking engagement with the'respective' gears. Selection means, for example including a cam follower, is employed for imparting longitudinal motion in either direction to the sleeve thus to engage either gear- [4 orgear l5 and lock the same tothe d'ri've'shaft. The cam follower conveniently is a centrally perforated metal disc- IT received on sleeve I6 and free for rotation between collars I8fixe'd to the sleeve.

The gears M and I fi'rnesh in power transmitting relation with corresponding gears 28' and 29 (Figs. land 2) which'are' fiiiedto respective ones of sleeves l9 and 2'0, co-axially'telescoped for relative rotation. The sleeve l9-' is-"supported in bearing l lc in the wall ofcasing H, and extends into gear bOX'ZZ through be'aring- 22) of the latter. Sleeve 20, on the'other hand;conveniently passes through the gear box, through bearing: lid in the casing wall, andco-airiallysupportscollar 3B J'ournalled in bearing 22-!) "ofthe gear box.

The bevel'gears-zl', 23"in' the gear box are connected'for rotating 'with the correspondingsleeves l9 and 2d; the collar 38, gear 23 and gear 28 conveniently being integral and keyed to shaft 20 asaunit. Pinions-26and 2'! carried by spider means, illustratively ineludin'g' the gear b02522 and stub shafts 26a, 21a, join' the bevel Z! and 23' thereby forming with the same" an epicyclic or differential gear.

The apparatus"ofthe'mechanism thus far described is conveniently traced from a suitable source'of power, as for example an operating electric motor which-drivesthrough a belt'and pulley system 24 soas to" impart clockwise rotation (as denoted by arrow'in Figs; 1- and 2) to the drift shaft 1-2; Assuming the'ge'ar M to be locked tothe drive shaft and gear l5 to be free of the clutch sleeve a's shown; a" counter-clockwise rota tion' is'tr'ansniitted through the power take-off gear 28 to-'sleeve-'2tl and bevel gear 23 of the differential gearing. With the gear box restrained against rotation'on" bearings 22); 229, as by stop mechanism to be described hereinafter, the bevel gear 23 drives pinicjns 26 and 21, thus imparting a clockwise rotationtotlie bevel gear 2-! and also to the related sleeve [Sand gear 29. The motion from'gear 29 is received-by the'meshing idler gear IS. The circumstances ass-ur'ned,- therefore; are such that'the-s-leeve [9- rotates in a clockwise direction and the co axial sleeve '2 t rotates counter-clockwise.

With" the drive shaft l-2 still rotating in the clockwise direction as before, and assuming the gear box to be held against rotation, but with gear l5 engaged by the clutch sleeve and gear [4 free of the sleeve, the gear 29 transmits a counter clockwise rotation to s'leevel9- and the related bevel 'gear 2|. This rotation is'rever'sedthrough pinions-ZG and Zhthe-bevelgear 23', sleeve Zllandgear ZB'aZccQrdin-gly rotate ina clockwisedirection.

Motion from gear 28 is received by gear [4 which now is an idler gear.

It will be seen that a general eiiect of operating the drive shaft in a constant direction of rotation and alternately selecting one of the gears l4 and I5 as the driving gear, is that of alternately rotating the sleeve [9 in one direction and then in the other while sleeve rotates in the opposite direction. This same effect, I find, is a highly useful measure in converting rotarymotion of the drive shaft l2 intb'recipiocatorymotion. In the present embodiment, sleeves l9 and 20 are simultaneously utilized for rotating threaded rods and threaded nut's'in oposite directions and, alternatively, in reversed opposite directions, as for example, threade'd'cylindrical rods SI, 32 and nuts 26a; 3541,3522 and 36a, to produce reciprocation. The rods 3|, 32 are disposed in co-axial relation to the sleeves. The rod 3|, illustratively, is considerably larger in diameter than rod 32. Both rods have'r'i'ght han'd threa'dedse'ction's and left hand threaded section's along the cylindrical surfaces thereof, the rig'ht hand threads being indicated by reference-characters 3Ia, 32a, and the El left hand'threa'cls' by 3'), 32b. There is a union or spline 33 (Fig; 5) connecting thethreaded shaft ends for relative longitudinal'movernent and for rotation as a unitary shaft. conveniently includes a grooved section 320 of the rod'32, and a bored' and internally featheredsection tlc of rod 3| into-which the grooved section telescopes and'fits. A similar connection is established by joint 34, in which the rod 31 is splined to sleeve IS for rotation therewith yet is free-for longitudinal displacement relative to the sleeve.

Each threaded section of the rods is in operativeengageihent with a'correspondingnut'wliich rotates with the power receiving sleeve 22']. In this sense, threaded section 3lb accommodates the" nut 20a,.which conveniently also forms an end of the power receiving sleeve 29 and is fixed-in longitudinal-positionalongwith the rest of the sleeve as by the journal in bearing The remaining nuts 35a on threaded section 3|a, 35b on section 32b, and nut" 36a on section 32a, are feathered for riding longitudinally in grooves 28 (represe'ntedby dotted lines-inFig. 1) in the inner surface'of sleeve' 20. By suitable means, the nuts 20 and a clockwise rotation to sleeve I 9; providedthe gear box 22 isrestrained. Thus, under these conditions, and with therods' and nutsoi the linear motion mechanisr-ri'ready'to-begin a stroke from the lower stroke position represented in Fig. 1, the power receiving sleeve 210' rotates all of the nuts 20a, 35a; 35b aridtta', in a counterclockwise direction; The" threaded rods 3i and 32, on which the nuts rotate, are themselves rotating,- this being in a clockwise direction determined by the clockwise motion of the power receiving sleeve retransmitted through joint 3% between the sleeve and rod and through union 33 between the rods. There ensues a highly positive and eflicient displacement wherein the The unfair; or jointt longitudinally fixed, but rotating nut 20a acts with threaded section 3171 of the oppositely rotating rod 3| to elevate the latter to the completed upper stroke position represented in Fig. 4. This upward displacement is possible in view of the spline type connection 34. Meanwhile, nut 35a is carried upward the distance con-- tributed by the action of nut 253a, and by engagement andopposed rotation with the threaded section em on the rod is driven upward a further amount corresponding to the threads traversed on the rod. Since nuts 35a and till) are held a constant distance apart and are respectively mounted on the rods 3i and 32, the upward movement of the nut 35a is transmitted to nut 35b and the corresponding rod 32. The rod 32 accordingly slides up as permitted by the union 33. In addition, the relative rotation of nut 5th and threaded section 32a advances rod 32 farther upward by an amount corresponding to the threads traversed. The upward advancement of the rod 32 meanwhile is accompanied by the H spective clockwise and counter-clockwise rotations of threaded sections 3m and nut 353a, which serves to elevate the nut and the related reciprocatory motion member 3b to top stroke position represented in Fig. 4. A coupling, including arm 38 adapted for idling in ball and cage bearings 39, is convenient for transmitting the longitudinal stroke of member 36 to reciprocative member iii without transmitting any rotation of the sleeve.

Upon driving the reciprocatory motion member .35 to top stroke position, the power receiving sleeves l9 and 2d are reversed in rotation promptly by shifting the clutch sleeve it from gear i i to coupling engagement with gear 15 and still maintaining clockwise rotation of the drive shaft I usually achieve this shifting action by automatic selector means synchronized with stroke of the reciprocatory movement, and preferabiy through freeing the housing of the differential gearing for rotation at the proper time, and relying upon the ensuing movement to effect the shift. Conveniently, for this purpose, a slide ii extends through opposite side walls of the casing I l and presents a bracket Ma for engaging buffer spring loaded detents 22a, 22b, 22c and 22d uniformly spaced on the circumference of the c i drical housing of gear box 22 and protruding from the wall. A cam path or groove 22c in the housing of box 22 (Fig. 2) receives the cam follower ll and has a sweep sufficient to shift the clutch sleeve IE on drive shaft l2 from driving or looking connection with one of gears Hi and i5 momentarily to interlocking engagement with both gears and then to driving engagement with the other for each quarter revolution of the housing. For synchronizing the initiation of the camming action just mentioned, with completion of strokes in the reciprocating movement of sleeve 36, there are suitably spaced stops Mb, tic fixed on the slide ii on opposite sides of arm 38.

It will be appreciated that by rotation of the differential gear as a unit while reversing any gear stroke of the reciprocatory movement, the threaded rod and nut combination is immediately relieved of related rotation and remains in neutral until the shift is completed. This enables accurate control over length of stroke of the reciprocating movement. Further the shifting of stroke direction is achieved with minimum stress since the rod and nut mechanism is not under working load once the differential gearing is released for rotation as a unit.

In the. present instance of operation let it be assumed that the gear box housing is held against rotation by detent 22a resting on bracket lla just before completion of the up stroke of sleeve 36. The sleeve in moving upward contacts stop llb thus carrying bracket 4 l a free of detent 22a. This frees the differential gear box for rotation, under which conditions bevel gears 2|, 24 and pinions 26a, 21a rotate as an interlocked unit all in the same direction with the power receiving sleeves l9 and 20 momentarilyunder the action of driving gears M, l5 and gears 28 and 29. Since the drive shaft I2 is rotating clockwise, the sleeves l9 and 20, differential gearing, and gear box 22 all rotate counter-clockwise substantially as a unit until detent 221) contacts the bracket 4 la. The rotation sweeps cam follower ll along path 22c and consequently sleeve l6 into engagement first with both gears l4 and I5, and then with gear l4, and meshing gear 28 now becomes the driving gear. As already described, the gear 5 for clockwise rotation of the drive shaft imparts a counterclockwise motion to sleeve I9 and a clockwise rotation to sleeve 20. Under these conditions the threaded rods 3! and 32 are driven clockwise and he corresponding threaded nuts are driven counter-clockwise This action serves to return the rod 35 through the longitudinally fixed and rotating nut 2M and joint 34 to lower stroke position represented in Fig. 1. The downward displacement carries nut 35a down a corresponding amount, and by engagement and opposed rotation with the threaded section 3| a travels down the rod to lower stroke position, also carrying along the nut 35!; as permitted by union is. The latter nut contributes in lowering rod 32 by travelling up threaded section 32a. As the rod 32 is lowered, nut Mia and member 36, arm 38 and reciprocative member it also are lowered. A further lowering action is produced by the nut 36a, by virtue of relative rotation with the rod.

Simultaneously with the reaching of lower stroke position, arm 38 forces down lug 41c and bracket Ma, thereby freeing detent 22b and consequently the gear box 22. Since the drive shaft i2 still is rotating clockwise, the sleeves l9 and 2% the differential gearing, and gear box 22 once more rotate counter-clockwise as a unit, this time,

until detent 220 contacts the bracket Ma. The rotation sweeps cam follower I! along path 22c, thus bringing sleeve Iii into drive shaft coupling relation with gear l5, which then drives the mechanism through an up stroke of reciprocatory motion in a manner already noted.

The Figs. 9 and 10 illustrate a modified drive for operating the sleeves i9 and 2!] in opposite directions and at different speeds thus to drive the threaded rod and nut arrangement more rapidly in one direction of stroke as compared with the opposite direction. The modification includes drike shaft l2 and related mechanism for transmitting power from a suitable source into the casing ll. There is a small gear l4 on the shaft in low speed gear train with relatively large gear 28; also large gear i5 is on the shaft in high speed operating connection with a smaller gear 29. The gears 28 and 29' illustratively are substituted to perform at different speeds the described functions of gears 28 and 39. I employ a sleeve i6 splined to drive shaft l2 for alternately coupling the gears M, iii to the source of power, while the other is released for idling. The sleeve illustratively includes friction plates l6'a, Hib for effecting the desired coupling through either of corresponding friction surfaces M'a, l5a of the gears. A suitable cam follower il, in bearings l8 emanate onthe. sleeve,:ridessin:cam pathl! 2a of the gearbox 22 for .alternatelydisplacing thesleeve 'ItO locking engagement withithe ;gears M" and l 5 to reverse the rotations of :sleeves -'|'9:and 220'.

:In Figs. 6, 'Land181thereisrepresented-a modified .form of power convertingmecihanism which instead of depending .uponlthe simultaneous oppositerotation of;thr.eaded.nuts.;and threaded rod means for producing reciprocation, achieves the reciprocatory motion Withsa diiferentia'l gear and sleeves 1.9 and :20 as before, but by the alternate procedures of..holdingfithecrelated=nuts 20a, 35a, 35b and 36a (Fig.1) .-:against rotation while rotating the threadedrods 31I.,-'32, and rtating the nuts while holdingxthe rods. "This-sequence of operations is effectively. and :efiiciently performed by alternately restraining. the sleeves 19 :and '20 against rotary ;motion' while .driving: the gear itselfin .aaconstant direction ofmotationas the motion transmitting means which: is selectively :op-- erativewith .the differential-gearing. The sleeves illustratively support respective levers 49 and 50, which extend :laterally :in:opposite directions and co-iunction with :detents ill and 352, respectively, for stoppingtheindividualsleeves. Adetent carriage including frame members 253, 54 which support the .detents 154,..52 .at: opposite. ends thereof to form a substantially. mectangular frame, -is axially .hinged at 53a, 54a :for rotation by means ofarm :55. Thedetent 5| comprises two substantially parallelholts 5-la.:.C-Eig;- 8.) interconnecting the frame membersl53 .and54. Each bolt 'accommodates a sleeve :51 b, =which is equipped with a fixedlug 51c and .isadapted for slidingmovement against the action 'of a buffer spring 51d. The lugson the sleeves are adjacent, and jointly present a surface for receiving and=holding lever 49. 'Detent 52 'isof similarconstructlon and is adapted for receiving -and' -holding the -lever '50 against rotation.

To reverse the stroke of reciprocatory motion developed by driving the gear box '22, "the diiTerential 'gearingtherein, and 'sleeve +9 =whil'e holdingsleeve 'by lever Hand'detent 51;,the detent carriage isrotated-to engage'lever 510 on sleeve f9 with detent 52. This serves to release lever '49 from 'detent "5.1 and consequentlyfrees the sleeve 20 ior'rotation. momentarily, there 'is a unitary rotation of sleeves 5.9;20 and "the differential gear, all in one directionby .virtueoi continualunidirectional driving of 'thehousingjof gear'box2'2" in the direction indicated'by.arrowjinl lig. .8. .Thus, lever 50 engages detent 5.2.,thereby restraining sleeve l5, and leaving. sleeve 20 .free for rotation under power from therotatingbox 22 and diflerential gearing therein. Therotationof'sleeve 20 reverses the stroke .of reciprocation. A.further reversal of stroke :is indicated by positioning the detent carriage to engage-lever and-tdetent '51. and free lever 50 and detent 52. .With'lever :50 free, there is once moreannitary .rotationof sleeves I9, 20 and .thedifierential-gear,.all-in one direction, assuming continued unidirectional driving of the gear box 22'. Theleverdfl then strikes detent 5 l, whereby further emotion. of. sleeve 2-0 is arrested and rotation. .ofxsleeve i9 continues throughout:thesreversedstroke.

.In automatically. operating the :motion converting mechanism of the present embodiment, the appropriate detentJB I l5-2'ziszswung to locking engagement with its .correspondingflever .49, i5fl under force transmitted'afromisleeve 36, arm 38 and lug 4 b or-4'lc andthrough'slidefl lito arm 55. This linkage is so adjusted: as to alternate the holding and release of levers iiiand 50, thereby alternately reversing the stroke of sleeve'31.

Referring to Fig. 11 of thedrawing, 'there is illustrated a form of-power transmitting system in accordance with my invention. In'the system, a suitable motor BIJ-is connected for 'opera'tinga reciprocative pump in well=65 through one of my motion converting mechanisms I'll connectedby means of reciprocative member 40 through 'well derrick linkage to'pump shaftB'S. 'Thewellderrick is equippedwith .an upstanding frame 5'] which supports a pumping arm 62, fulcrumed at 61a and connected atone end--to=the=pump shaft 66. A roller -63 connected in an articulated joint between adjacent ends of link-64 and reciprocative member 40 is guided in track 61. 'At opposite end, the link :64 is hinged to the pumping arm 5-2 and is of such length andso guided 'by'the'roller 63 as to transmit-an up and a down stroke to the pumping arm, and consequently to the'pump, for each single stroke from the mechanism 4 0.

It will be appreciated that'while the mechanism for-converting rotary motion, as hereindescribed, is highly suited for the output of alternately reversedstrokes of reciprocation of constant amplitude, the mechanism'may benrevers'ed *asdesired along the length of any given stroke, as'by manual or automatic control applied to slide M '(Figs. '1 and 6) or may be stopped and 'started oncemore, to continue in a given direction, as byrstopping the drive 2:3 and then resuming the driveinthe same-direction as before.

While two telescoping threaded rods have been described for coaction'with threaded nuts .for achieving reciprocatory motion in therembodiment hereinbefore set :forth, it will 'be understood that a single threaded rod may be semployedsin conjunction with one or more nuts for coacting therewith for producing linear motion or reciprocation.

Since many possibleembodimentsmay be made of my invention andsince many changes may be made in the embodiments'hereinbefore set forth, it will be understood that all matter described herein, or shown in thedrawings, .is to be interpreted as illustrative and not as a'limitation.

I claim:

1. In mechanism for converting rotary motion to reciprocating linear motion, the -'combination which includes, motion converting means comprising at least two engaging threaded members mounted for relative rotation and co-action "to produce linear-displacement'of=one of them, gearing means connectivewith-saidthreadedmembers for transmitting opposite driving rotation to the same to direct thedisplacement, and means controlledby movement of said menibertoreverse the direction of rotation-of both' said members.

2. In mechanism for convertingrotary motion to linear motion, the combination which-includes, motion converting means lcomprising at leasttwo engaging threaded-members mounted for relative rotation and co-action to 'produce linear displacement of at least oneof them, differential gearing having a pair-of difierentialgears .eachiconnected for rotation with one :of' :said athreaded :members, andmeans for selectively coupling :the differential gears to rotary drive means :of .fixeddirection .rotation.

3. In mechanism for converting :rotary :motion to reciprocatory motion, .the icomhinationrwhich includes, motion converting means. :comprising: at least two engaging threaded :members mounted for relative rotation and co-action 'to produce ;re-

7 .ciprocation :of 0118 of them,;sdifierential gearing 9 having corresponding gears thereof connected for driving the corresponding ones of said threaded members, and means for alternatively coupling said corresponding gears to a rotary drive source of fixed rotation, and a pinion between said corresponding gears mounted on a normally fixed axis.

4. In mechanism for converting rotary motion to reciprocatory motion, the combination which includes, motion converting mechanism comprising at least two engaging threaded members mounted for relative rotation to produce displacement of at least one of them, mechanism for simultaneously transmitting opposite rotations to said threaded members to achieve the displacement and means dependent on the amount of said displacement in either direction to reverse the direction of said rotations.

5. In mechanism for converting rotary motion to reciprocatory motion. the combination which includes, motion converting mechanism comprising at least two engaging threaded members mounted for alternately reversed opposed rotation to produce reciprocation, drive means operating in a constant direction, means connecting said drive means for alternately rotating said threaded members in opposed directions, and gear means for interconnecting the threaded members in opposed rotary relation during operation of said drive means.

6. In mechanism for converting rotary motion to linear motion, the combination which includes, dilferential gearing, unidirectional rotary motion transmitting means selectively operative with said differential gearing for driving through opposite sides of the same, and two members each connected for simultaneous rotation with one of the opposite sides of said. differential gearing and mounted for co-action to produce linear displacement.

7. In mechanism for converting rotary motion to linear motion, the combination which includes, differential gearing, unidirectional rotary motion transmitting means selectively operative with said differential gearing for alternately driving through opposite sides of the same, at least two engaging threaded members each rotatable with one of said opposite sides of the differential gearing and mounted for co-action to produce linear displacement, and selective means actuated by movement of one of said threaded members for engaging said unidirectional motion transmitting means to driving reiation alternately with one or the other of said opposite sides of the differential gearing thus for producing reversed strokes of reciprocation with said threaded members,

8. In mechanism for converting rotary motion to recipricatory motion, the combination which includes, differential gearing comprising opposed gears and at least one interconnecting pinion for the same, unidirectional rotary motion transmitting means selectively connective with the differential gearing alternately through said opposed gears, at least two engaging threaded members rotatable each with one of the opposed gears of the differential gearing and mounted for coaction to produce reciprocation, and selector means for automatically setting said unidirectional motion transmitting means to driving relation with the differential gearing alternately through said opposed gears thus producing alternately reversed strokes of reciprocation with said threaded members, said selector means including means for restraining the axis of the interconnecting pinion of said differential gearing 10 from rotation about the axis of the opposed gears throughout the individual strokes of reciprocation and intermittently releasing the same to actuate said selector means for reversing stroke.

9. In mechanism for converting rotary motion to reciprocatory motion, the combination which includes, difierential gearing, unidirectional rotary motion transmitting meansselectively operative with said differential gearing for alternately driving through opposite sides of the same at dififerent speeds, at least two telescoping threaded members rotatable each with one of said opposite sides of the differential gearing and mounted for co-action to produce reciprocation, and selector means for engaging said unidirectional motion transmitting means alternately to driving relation with said opposite sides of the differential gearing thus for producing alternately reversed and differently speeded strokes of reciprocation with said threaded members.

10. In mechanism for converting rotary motion to reciprocatory motion, the combination which includes, differential gearing, unidirectional rotary motion transmitting means selectively connective with said differential gearing for driving through axially opposite sides of the same in alternately reversed directions, at least two telescoping threaded members rotatable each with one of said opposite sides of the differential gearing and mounted for co-action to produce reciprocation, and selective means automatically setting said unidirectional motion transmitting means alternately to driving relation with said opposite sides of the dififerential gearing thus for producing alternately reversed strokes of reciprocation with said threaded members.

ll. In mechanism for converting rotary motion to reciprocatcry motion, the combination which includes, differential gearing, including opposed differential gears and a pinion unidirectional rotary motion transmitting means selectively operative with said differential gearing for alternately driving opposite gears of the same in the same direction, selective means for automatically engaging said unidirectional rotary motion transmitting means alternately to driving relation with said opposite gears of the differential gearing and means to lock the pinion against rotation about the axis of the gears when driving either of them.

12. In mechanism for converting rotary motion to reciprocatory motion, the combination which includes, differential gearing comprising opposed gears and at least one interconnecting pinion for the same, unidirectional rotary motion transmitting means for selectively driving the differential gearing through said opposed gears, and means for restraining the axis of said interconnecting pinion from rotation about the axis of said gears and releasing the same only during selection of the driving relation between said unidirectional rotary motion transmitting means and the difierential gearing.

13. The mechanism as defined in claim 3 in which means is provided to release the axis of said pinion upon a predetermined stroke of the reciprocable threaded member.

14. The mechanism as defined in claim 4 in which each of the threaded members is formed in at least two parts telescopically and non-rotatively secured together.

15. The mechanism as defined in claim 11 in which mechanism is provided to release the pinion during the change of drive.

16. The mechanism as defined in claim 15 in

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