US2881866A - Brake means - Google Patents

Description

R. H. HILL BRAKE MEANS April 14, 1959 5 Sheets-Sheet 1 Filed Dec. l0, 1953 .nl ll|L.Pl|| ,lll llllllllll Til.,

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BRAKE MEANS April 14, 1959 Filed Deo. l0, 1953 5 Sheets-.Sheet 2 R. H. HILL BRAKE MEANS April 14, 1959 5 Sheis-Sheet 3 Filed Dec. 10,v 1953 IN VEN TOR.

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United States Patent BRAKE MEANS Robert H. Hill, Fort Wayne, Ind., assignor, by mesne assignments, to Perfect Circle Corporation, Hagerstown, Ind., a corporation of Indiana Application December 10, 1953, Serial No. 397,293

17 Claims. (Cl. 188-69) This invention relates generally to pumping apparatus for use in oil wells or the like and more particularly to novel means for preventing loss of tluid head when the pumping apparatus is stopped.

`Oil well pumps of the reciprocating type are usually provided with a foot valve or check valve Iadjacent the intake .of the pump in order to prevent loss of the fluid head of oil from the pump and production tubing both during operation of the pump and during a period when the pump is stopped for any reason. However, there are frequent occasions where the oil or other fluid being pumped contains objectionable quantities of abrasive material, such as sand, with the result that any conventional valve structure which may be provided at the intake end of the pumping apparatus is subject to severe erosion and consequently has a short life.

In the pumping apparatus of the present invention, the conventional foot valves or checkvalves are entirely eliminated so that the apparatus can readily handle abrasive material. Nevertheless, it is still desirable to make adequate provision for preventing loss of fluid head when the pump is stopped for any reason. Furthermore, it is frequently desirable to utilize a reversible pumping apparatus so thatuid can be pumped downwardly into the well for forcefully flushing the producing formation. Obviously, with such a reversible pumping apparatus the elimination of the conventional check or foot valve arrangement is necessary in order to permit the desired reversible operation.

Accordingly, a primary object of the invention is to provide novel means in a pumping apparatus for preventing loss of fluid head when the pump is stopped.

Another object of the invention is to provide a novel reversible pumping apparatus for use in oil wells or the like and including ilow control means for preventingloss of fluid head.

A further object of the invention is to provide a novel combination of a reversible pumping apparatus and means for preventing lossof fluid head without the use of conventional valve structure.

Other objects land advantages of the invention will become apparent from the subsequent detailed description taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is an elevational view on a reduced scale of a complete oil well pumping apparatus embodying the features of my invention and showing the apparatus in position in the well casing;

Fig. 2 is a fragmentary vertical sectional view on an enlarged scale of a portion of the apparatus illustrated in Fig. 1;

Fig. 3 is a fragmentary vertical sectional view on a still further enlarged scale showing a portion of the apparatus illustrated in Fig. 2 in one of its operating positions;

Fig. 4 isa view similar to Fig. 3 but showing the apparatus in a different operating position;

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Fig. 5 is a transverse sectional view on a reduced scale taken along the line S--S of Fig. 3;

Fig. 6 is a fragmentary transverse sectional view look ing upwardly along the line 6 6 of Fig. 3; y

Fig. 7 is a fragmentary transversesectional view looking downwardly along the line 7-7 of Fig. 3, and

Figs. 8 and 9 are diagrammatic side elevational views of a portion of the apparatus illustrating lan operating principle of the invention.

Referring first to Fig. 1, the fragmentary lower portion of an oil well casing 11 is shown with the surrounding earth formation being` indicated at 12.. It will be understood that the casing 11 extends in the usual manner from the ground level to the bottom of the well although neither of the extreme ends of the casingare illustrated in the drawing. The pumping apparatus embodying the features of my invention is shown in position in the well casing and comprises a plurality of sec` tions connected in end-to-end relation for ilu-id vlow therebetween.

At the top of the apparatus is a valve section A which includes a check valve and a drain valve.` The 'check valve is normally not in use but can be put into operation in order to facilitate starting of the apparatus under heavy load. The drain valve may be of the sleeve type for permitting oil to be drained from the tubing into the well casing when necessary in order to prevent the pulling of a wet string. The function of the valve section A is not particularly related to the operation of the remaininder of the apparatus and the details thereof do not form any part of the present invention. Reference is made to my copending application Serial No. 319,995, led November 12, 1952, now Patent No. 2,752,861, for a more complete disclosure of this portion of the apparatus.

Below the section A of the pumping apparatus is a pressure balancer or equalizer section designated at B for regulating the pressure of the transformer oil in the motor compartment. Next below the section B is a section designated at C which includes a brake and an actuating solenoid which are hereinafter described in detail since they comprise the principal feature of the present invention. A reversible motor section D, comprising in this instance a pair of induction motor units 13, is disposed 'below the section C and is connected to a reversible pump section F by means of a universal coupling section E. A cable 14 comprising the electrical conductors for supplying electrical energy to sections C and D is also provided and extends downwardly from the ground level through the casing 11 and enters the apparatus at section B as shown. g

Although the invention has broad utility, it is illustrated herein in connection with a reversible pumping apparatus so that in one direction of operation oil can be pumped upwardly from the well and in the opposite direction of operation oil or other iluid can be forced downwardly into the well under pressure. Thus, during production the reversible motor section D is operated so that the reversible pump section F draws oil from the bottom of the well casing and discharges the oil through suitable passageways provided in sections A to E for discharge through a tubing string 16 which is connected to a tank or other storage facilities at the ground level. When the producing formation or the intake to the apparatus becomes clogged or obstructed to an objectionable degree, as indicated for example by a low volume of oil at the bottom of the well, a suitable expansible packer .section .G is provided. In this instance, a `packer 17 of the bottom hole type is shown connected at the inlet end of the pump section F but it will be understood that a .side wall packeror -any suitable packerl of a Itype adapted to resist upward pressure may also be utilized. A iluid intake 18 in `the form of a length of perforated or .slotted pipe is shown in ybroken lines and it will be understood that this fluid intake is connected below .the .packer 17 or in place thereof in the event that ya side wall packer is utilized.

In the embodiment shown in the `drawing by way of illustration, the packer 17 is of a conventional type including an axially compressible rubber sleeve which is lretracted as initially installed in the well casing. However, by means of a telescoping action, well known in the packer art, .slidable .sections of the pump -casing are shifted after lthe apparatus is .in place in the well and the rubber sleeve is compressed .and `bulged outwardly `into tight-tting sealed relation with the inside of the casing 11. In this manner, it will be understood that the packer 17 effectively segregates the lower portion of the well so as to define a :reservoir space between the packer and the bottom of the well. Thus, when oil or other purging fluid is pumped downwardly into the Awell vunder pressure, :the reservoir space is sealed at its upper end by lthe packer 17 and the .oil is therefore readily forced under high pressure into the obstructed producing Aformation or strata for purging ,and cleaning the same. At the same time, the pump intake '1'8 is also cleaned and -hushed out. .As also seen in Fig. l, the invention is illustrated in connection *with a reversible positive displacement pump ofthe Moyno type. Thus, in section F of the apparatus .there is shown .an elongated female helical member 19 which constitutes the stator of the pump and an elongated `male helical member 21 mounted within the female member and .constituting the rotor of the pump. The Outer member .or stator 19 is provided with one helical thread more than the inner member or rotor, and the two members are so arranged .and shaped that every thread vof the rotor iis constantly in contact with the stator in any transverse section through the pump. This relation of the rotor and stator is such that a plurality of closed spaces or cavities are defined between the two members 'because of the vdifference in the number of threads on each member. When the rotor is rotated relative to the stator, the cavities .or spaces between the members are displaced in a longitudinal .direction with the result that a uid material vcan be axially transported between the WO members to lobtain the desired pumping effect. Ref- ,ereutleis ,rnadeto U.S. Patents Nos. 1,892,217 and 2,028,- 40.7 vfor aldetailed consideration of the theory and operation of the progressing .cavity or 'Moyno type pump.

Referring now to Figs. 2 to 9, the primary novel `features of the invention will be described in connection with the detailsof the solenoid and -brake section C. As `previously mentioned, inthe -present invention the lower .or inlet end of :the apparatus is not provided with any special foot or check valve arrangement to prevent loss of fluid head from the system. 'The elimination of such conventional intake Valve structure is desirable in order .to facilitate reversible .operation lof the apparatus, as 'hereinbefore described, -and also to permit the pumping apparatus to `be utilized even where the oil or other fluid .being pumped contains appreciable amounts of abrasive material such .as sand which would vhave a detrimental erosive effect on ordinary `valve structures. However, when the valve structure at the intake end of the pump is eliminated, it is fstill desirable to -makesome provision 'for preventing the loss of uid head when the pump'is stopped jfor any reason. For example, Iif the pump Vis stopped during a production period, it will `be seen that the hydrostatic pressure of the head of loil inthe produc- :tion `tubing `16 above the pump will tend to force oil y.downwardly `through the pump causing the llatter to motor with consequent loss of fluid head. According to the present invention, I prevent such -undesirable motoring of the pump by utilizing a suitable brake which holds the pump rotor 21 in xed position relative to the stator 19 whenever the motor and pump are stopped for any reason. Obviously, the very nature of the Moyno pump is such that leakage of oil or other fluid back into the well through the pump will be prevented as long as the pump rotor 21 is held against rotation.

As seen in Fig. 2 the upper end of the rotor shaft of the motor, `designated at 2 2,'extends upwardly through a bearing 23 mounted in a partition or brake housing structure 24. A cup-shaped rotatable member 26, comprising one of a pair of complementary brake members, is keyed to the upper extremity ofthe rotor shaft 22, the shaft extending upwardly through the base of the cupshaped member 26 and being provided with a washer 27 Iand a lock nut 28 for further rigidly securing the brake vmember 26 on the rotor shaft 22 of the motor. Thus, the brake member 2,6 rotates with the shaft `22 but is held against'axial movement. l'The upper annular edge of the cup-shaped brake member k26 is serrated or notched to lprovide a plurality of dogs or Ateeth 29 as hereinafter described in detail.

A complementary brake member is provided in the form of an inverted generally cup-shaped member 31 disposed in opposed coacting relation above the brake membei 26. The brake member 31 has a tubular extension 32 in lwhich is slidably received an elongated actuating member 33 having an enlarged head portion 34 disposed within the cup-shaped member 31 for supporting and actuating the latter as hereinafter described in detail. As will also be described in greater detail hereinafter, the lower annular edge of the brake member 31 is 'likewise serrated or notched l-to provide a plurality of dogs or teeth 36 adapted to -be engaged with the teeth 29 on the complementary `brake member Y26. y

The housing 24 extends upwardly to provide a generally 4tubular wall portion 37, and a plurality of radial pins 38 project outwardly from the brake member 31 for coast-ion with the housing. The housing 24-37 is held against rotation by being secured by means of screws 35 yto a solenoid housing 40 which is in turn rigidly held in the apparatus casing. As best yseen in Figs. `3 to 5, the pins 38 have a threaded connection, as at l39, in the wall of the cup-shaped brake element 31 and carry annular resilient cushions or shock absorbers 41 of rubber or the like, -the'rulfiber cushions being secured on the pins 38 between 'a pair -of concentric supporting bands or rings 42 and 43. As will be evident particularly 'from Fig. 5., the pins extend rigidly'from the brake member 31 `through elongated vertical yslotted portions 44 provided in ,the tubular wall 37 of the `fixed housing. Consequently, it will be readily understood that the brake member 3,1 is substantially held against rotary movement but can undergo a slight deflection in a vrotary direction by reason of the resilient rings or cushions 41 interposed between the retaining pins 38 and the walls of the grooves or slots 44 provided VVin the housing 37. Moreover, it will yalso be vseen that by reason of the vertical elongation of the slots 44, the uppermost brake member 31 can undergo limited vertical axial movement both in conjunction with and relative to the elongated actuating member 33 for effecting `engagement `and disengagement between the teeth or dogs -29 and 36 of the respective clutch members. Thus, upon upward movement of the member 33, the uppermost brake member 31 will be lifted lupwardly to effect release of lthe device. lUpon .downward movement 4or release of the actuating member 33, the brake member 31 is free to move `downwardly kinto .braking engagement with the brake vmember 26. A coil .spring 46 is provided for normally 'urging the brake `member 31 downwardly into engaged `relation with the opposite brake member 26, the spring 46 coacting be.- tween the upper `end of the brake member 31 Iand a shoulder portion 47 .on .the housings?,

:For eiectng shifting movement of the upper brake member 31, a solenoid 48 is mounted above the' brake mechanism in its housing 40 and includes an energizing winding as well as a shiftable plunger. A connector 49 having a swivel connection with the plunger of the solenoid is threadedly attached and locked, as at 51, to the upper end of the actuating member 33 for operating the latter. Although the circuit connections are not shown in the drawing, the energizing winding or coil of the solenoid 48 is preferably connected in circuit with the electric motor section D and a plurality of conductors 52 so that Whenever the motor is in operation the solenoid 48 will be energized and the actuating member 33 will be held in its uppermost position with the brake member 31 thereby being lifted into disengaged position. However, if the current to the motor is interrupted for any reason so that the operation of the pump ceases, it will be seen that the brake member 31 will be immediately released by the solenoid 48 and the spring 46 will then force the brake member 31 into braking engagement with the lower brake member 26. With the rotor shaft 22 of the motor thus held against movement by the brake mechanism, it will be understood that the pump rotor 21 cannot rotate and consequently it is impossible for the llud head above' the pump to flow through the pump structure. In other words, the pump itself then serves as a valve and there is no opportunity for the fluid pressure exerted by the hydrostatic head to effect motoring of the pump with consequent drainage of the iiuid to the bottom of the well.

In order to maintain a proper coaxial relationship between the upper and lower brake members 31 and 26, I also provide an annular bushing 53 (Figs. 3 and 4) which has a rigid press fit within the upper cup-shaped brake member 31. 'Ihe bushing 53 is of sucient axial length to extend downwardly within the lower cup-shaped brake member 26, and the lower end of the bushing 53 is formed with a guiding lip or bead 54 which extends circumferentially around the bushing in sliding engagement with the inner periphery of the brake member 26. Thus, at all times the necessary coaxial relationship between the brake members 31 and 26 is maintained so as to insure proper engagement and disengagement of the respective brake teeth.

As will be evident from the foregoing description, the guide bushing 53 provides a telescopic sliding relation between the respective cup-shaped brake members 31 and 26 so that axial shifting movement of the upper brake member 31 with its rigidly attached bushing 53 relative to the lower brake member 26 is in effect a piston and cylin der arrangement. As is usual in motors of this type, the motor section D contains a suitable uid such as a transformer oil, and this oil is also present throughout the solenoid and brake section C and the pressure equalizing section B. Thus, the entire brake mechanism is surrounded or immersed in the transformer oil. Because of the telescopic or piston and cylinder operating relation between the respective brake members, as just described, it will be seen that the transformer oil which is confined between the cup-shaped brake members 31 and 26 exerts a damping or cushioning action in the manner of a dashpot so as to slow down the downward movement of the brake member 31 under the action of the spring 46. The displacement of the conned transformer oil during downward movement of the brake member 31 toward the brake member 26 is controlled, in this instance, by providing a predetermined clearance between the guide lip or bead 54 and inner periphery of the brake member 26. For this purpose, the lip or bead 54 is formed with a plurality of ats 56 (Figs. 3 and 7) so that the displaced uid may be forced from between the brake members at the desired rate.

The dashpotor damping action during braking move ment of the upper brake member is important for most satisfactory operation of the apparatus because of the fact that the brake is of the dog type. In other words,

during operation of the apparatus the rotor shaft 22 of the 'motor is rotating at a very `high speed andthe damping or dashpot action for delaying the engagement of the brake is necessary in order to permit the rotor shaft 22 to slow down after the current supply to the motor has been interrupted. If an attempt were made to engage the brake members during high speed rotation of the rotor shaft 22, it will be readily apparent that excessive shearing forces would be exerted on the brake teeth and also on'the retaining pins 38. Consequently, the delayed braking action is a highly desirable feature of the invention.

Referring particularly to Figs. 3 and 4, the general operation of the brake mechanism will now be described. In Fig. 3 the device is shown in running position, i.e., with the motor and pump in operation. Thesolenoid 48 being energized by the same source of electrical energy which energizes the motor, it will be understood that the actuating member 33 is retained in its uppermost position with the upper brake member 31 being supported on the enlarged head 34 and thereby held in lifted or disengaged position.

In Fig. 4, the brake'mechanism is shown in engaged position aftervthe motor has been stopped. When the current supply to the motor and the solenoid 48 is interrupted, the actuating member 33 falls by gravity until the head portion 34 rests on the upper end extremity of the rotor shaft 22 thereby releasing the brake member 31. With the brake member 31 thus released, the spring 46 forces the brake member downwardly but the movement is damped or slowed by the dashpot action hereinbefore described due to the restricted displacement of fluid from between the vbrake members. In the meantime, of course, the rotation of the rotor shaft 22 with the brake member 26 mounted thereon has slowed` down considerably,'and finally the desired engagement between the brake teeth is accomplished. At the instant of braking engagement, any rotary force imparted to the brake member 31 is absorbed by 'reaction of the cushioned pins 38 against the walls of the slots 44. With the brake teeth in engagement as shown in Fig. 4, it will be understood that the radial retaining pins 38 hold the entire mechanism, including the pump rotor 21, against rotation.

When the current supply to the motor and solenoid 48 is again restored, the rotor shaft 22 tends to rotate and simultaneously the solenoid 48 lifts the actuating member 33 upwardly and the upper brake member 31 is ultimately lifted out of engagement with the lower brake member to permit free rotation of the latter. It will be understood that even when the brake members are engaged as in Fig. 4 there is a very slight clearance between the respective teeth 29 and 36. Consequently, it will be seen that if the motor is operating in a given direction, is then stopped so that the brake engages, and is subsequently started up again in the reverse direction, the slight edgewise clearance between the brake teeth will permit a very slight degree of reverse rotary movement of the lower brake member 26, and in this instant the upper brake member 31 can readily be retracted axially with minimum resistance. In other words, a reversal in the direction of operation of the pump during a start-up permits the clutch to be disengaged with a minimum load or frictional resistance between the brake teeth.

However, it will be also appreciated that if the pumpis restarted in the same direction of rotation, the initial frictional resistance between the brake teeth is maintained and consequently the upper brake member must be retracted under maximum load. In order to overcome any tendency for the brake mechanism to stick when the pump is thus restarted in the same direction, I preferably employ a solenoid 48 of the heavy duty type suflicient to overcome the frictional resistance tending to hold the brake ,members :in .engaged relation- '.In addition. Ait will be seen that .the :actuating member 3.3 has .a sliding relationship in .the tubular extension 3.2 ct the upper brake member 31 .and yas ta result there is a lost motion relation between the .head portion 34 of the Aactuating member 33 and .the underside er base of .the brake member 31. Thus, vin Fig. 4, when .the .solenoid 4,8 .is actuated it will be .seen .that the .actuating member 33 is lifted upwardly and gains `.considerable momentum during the time in which ,the head portion 34 travels from its position of rest on vthe .end of the rotor shaft 22 into impacting engagement with the brake member 31. The delayed impact 4or hammer .blow thus imparted to the brake member 3.1 assists materially in disengaging the brake member 3.1 under load and :thereby overcomes any tendency toward sticking.

As seen ,in Figs. 3 vand 4, the upper brake member 31 also has a .pair of apertures or bores 58 which arenormally closed by a. pair of cap screws 5.9. These screws 59 may be removed when necessary to permit insertion vof a .pin

.or other tool in order to `eject .the press-fitted guide bushing S3 from the brake member 31 thereby facilitating repair or maintenance of the device. Also, inthe event that it is desired to minimize the dashpot action .between the brake members 31 and 26, it will be seen .that .the removal of one -or .both .screws 59 will allow more rapid Vdisplacement of the .conned oil .during braking ,movement ofthe member 3,1 and thereby decrease the extent of damping action.

jIn the foregoing description it was pointed out that the dashpot or damping action as a result of the presence of transformer oil slows .down the axial shifting Ymovement of the upper brake member 31 so .as to provide ample time vfor proper reduction in the speed of rotation of the rotor ,shaft 22 before the upper brake mem- -bcr 3,1 attempts to .engage with the lower brake member 2 6. Because of the very slight clearance between .the respective teeth -of the brake members, the desired degree of register between the teeth for Ybraking engagement requires that the rotor shaft 22 be almost entirely stopped. 'In order to insure this result, I have .shown (Figs. 6-9) the teeth 36 on the upper brake member 31 with beveled or slanted corner edges, as at 7. These beveled corner edges function as cam surfaces so as to produce an upward rebound of the upper brake member 31 whenever the beveled edges .57 are engaged by the corresponding corner edges of the teeth 29 on the rotating lower brake member ,26. Thus, in Fig. 8 the upper brake member 31 is` shown in downwardly moving relation, as `indicated by .the arrow, and the lower brake member 26 .is still rotating in the direction indicated by the arrow. ln. the situation shown in the drawing, the teeth 36 ,on the upper brake member 3.1 are descending in non-registered relation with respect to the spaces between .the teeth ,29 on the lower brake member 26. Consequently, :aS .5.66.11 in Fig. 9, the right hand `,corner edges. .of .the teeth as on the rotating lower brake member .2 6 strike all. impacting blow against the vleft hand beveled corner edges 57 of 'the teeth 36 on the upper brake member 3l whereupon the latter is caused to rebound upwardly. This rebounding impact between the respective .teeth is repeated Aagain and lagain until such time as the speed of rotation of the -brake member 26 is reduced su'ciently so that thedownwardly urged brake member 31 can enter into .clutching engagement with the lower brake member 26 when the respective toothed portions thereof are in substantially exact register. Obviously, this same rebound elfect will be realized during reverse operation of theapparatus but the rebounding impact will take place in this c'ase between the `vleft hand corners ofthe teeth 29 and the right hand beveled corner edges 57 ofthe vteeth 36.

:Although the invention has -been described -in connection vwith .a certain specific structural embodiment thereof, it will be .understood that various modications vand .equivalent Structures may be resorted to without depart- .ing from .the scope. ofthe .invention as. :dened :in the Lapnended'elaims- :I claim:

1,. Brake means lfor holding amember :rotatably driven inone .direction ,against rotation in the opposite direction when the driving 4means therefor is de-energized, comprising a Stationary housing, a pair of coaxial brake members `mounted in coacting relation within said housiing and having cooperating teeth, one of said brake members being adapted to .be operatively connected to the driven member for rotation therewith and the other of said brake members being non-rotatable but axially shiftable .toward and away from the rotatable brake member yfor effecting .engagement and ldisengagement therebetween, at least one ,retainer element yextending outwardly from l,said shiftable brake member `i-nto coacting engagement with said housing for preventing rotation of said .shiftable brake member about said axis, resilient cushioning means ,interposed Vbetween said retainer element and the coaoting portion of said housing, spring means normally urging the shiftable brake member into braking engagement with the rotatable brake member, each of the teeth on one o f said members having beveled corner edges for effecting axial rebound of .said non-rotatable member during rotation of said rotatable member when said-teeth are .not in register for braking engagement, and means `for retracting the shiftable brake member from said .braking engagement in response to lenergization of the driving means yfor the rdriven member.

2. Brake means for holding a member rotatably driven in one direction against rotation in the opposite `direction when the driving means therefor is dre-energized, ycomprising a stationary housing having a plurality of vertical elongated slots, a pair of upper and lower brake members mounted lcoaXially in coacting relation within Seid housing, :the lower of said brake members being adapted to `be, operatively connected to the driven Amember for rotation therewith and the upper of said brake members being non-rotatable but axially shiftable toward and `away from the lower brake member for effecting engagement `.and disengagement therebetween, a plurality of retainer pins -extending radially from said upper rbrake member and projecting into said vertical slots in said housing for preventing rotation of said upper brake member :about said axis, .the vertical elongation of said slots permitting .up-and-down movement of said upper brake member, spring means normally urging the shiftable brake member into braking engagement with the rotatable brake member, and means for reti-acting the shiftable brake member from said braking engagement in response to lenergization of the driving means for the driven memer.

3.. Brake means for holding a member rotatably driven in one. .direction against rotation in the opposite direction When :the driving means therefor is de-energzed, omprising a stationary housing having a plurality of -vcrtical elongated slots, a pair of upper and lower generally .Ctlp-.Shaped members mounted coaxially in opposed coacting relation and 'having their annular edges provided with ,cooperating teeth, said lower cup-shaped member being adapted to .be operatively secured to the driven member for rotation therewith and said upper cup-shaped member being held against substantial rotation and being shifta'bly mounted for axial up-and-down movement for effecting lengagement land disengagement between the respective teeth, a plurality of retainer pins extending radially from said upper cupshaped member and projecting into `said slots in said housing for preventing rotation of said fupper cup-shaped member, the vertical elongation of .said slots permitting up-and-down shifting movement of said upper member, resilient cushioning elements interposed between said pins and the sides of said slots, spring means coacting between said housing and said :upc per cup-shaped member for normally urging the .latter downwardly into braking engagement with the lower cup-'shaped member, and means' for retracting Ysaid upper cup-shaped member upwardly and out Aof said braking 'engagement in response to energization of the driving when the driving means therefor is deenergized, comprising a pair'of upper and lower generallycup-shaped memvbers coaxially mounted in opposed coacting relation and having their annular edges provided with cooperating teeth, said lower cup-shaped member being adapted to be operatively secured to the driven member for rotation therewith and said upper cup-shaped memberbeing held against substantial rotation and being shiftably mounted for axial up#anddown movement for eiecting engagement and disengagement between the respective teeth, a guide bushing rigidly mounted in one of said cup-shaped membersA and extending coaxially into the other of said cup-shaped members for maintaining coaxial relationship between saidmembers, spring means coacting with said upper cup-shaped member for normally urging the latter downwardly into braking engagement with the lower cup-shaped member, means operable in response to engaging movement of said member for retarding meshing engagement untilfrotation of said rotatable member has substantially stopped, and means for retracting said upper cup-shapedmember upwardly and out of said braking engagement in response to energization of the driving means for the driven member. v

5. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means'therefor is deenergized, comprising a pair of coacting brake members having cooperating teeth, one of said members being adapted to be operatively connected to the driven member for rotation therewith and the other of said members being held against substantial rotation, one of said brake members also being shiftable into and out of braking engagement with the other of said brake members, means normally urging the shiftable brake member into braking engagement with the opposite brake member, releasing means for disengaging the shiftable brake member in response to energization of the driving means for the driven member, and means operable in response to engaging movement of said shiftable member for retarding the movement of said shiftable brake member into meshing engagement until rotation of the rotatable brake member has substantially stopped.

6. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means therefor is deenergized, comprising a pair of brake members, one of said brake members being adapted to be operatively connected to the d riven member for rotation therewith and the other of said brake members being held against substantial rotation, housing means for maintaining a tluid around and between said brake members, actuating means for eecting relative movement between the brake members for engaging and disengaging saidbrake members, and means providing a telescopic sliding piston and cylinder arrangement including a restricted passage for by-passing said Huid and operable upon said relative movement to displace the fluid between said brake members and thereby damps and retards the. relative movement between said brake members during braking engagement thereof.

7. Brake means for holding a member rotatably driven in one direction against rotation in lthe opposite direction when vthe Adriving means therefor is deenergized, comprising a pair of coaxial toothed brakemembe'rs,

one of said brake members being adaptedto A,be operatively connected to the drivenmember for rotation therewith and the other of said brake members being non-rotatable but axially shiftable toward and away from said one brake member foryeffecatingengagement and disengagement of the toothedportions of s'aid brake 10 members, housing means for maintaining'uid around and between said brake members, spring meansmormally 'urging said other brake member into braking engagement with said one brake member, and means for retracting said other brake member to effect disengagement in response to energization of the driving means for the driven member, said brake members having cooperating piston and cylinder portions thereof in telescopic sliding relation and including a restricted passage for by-passing the fluid, said portions displacing the uid between said brake members through said passage upon the movement of said other brake'member toward said one brake member, thereby damping and retarding said braking movement.

8. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means therefor is deenergized, comprising a pair of upper and lower generally cupshaped members mounted in opposed coacting relation and having their annular edges provided with cooperating teeth, said lower cup-shaped member being adapted to be operatively secured to the driven member for rotation therewith and lsaid upper cup-shaped member being held against substantial rotation and being shiftably mounted for axial up-and-down movement for eifecting engagement and disengagement betweenthe respective teeth, spring means coacting with said upper cup-shaped member for normally urging the latter downwardly into braking engagement with the lower cup-shaped member, means for retracting said uppercup-shaped member upwardly and out of said braking engagement in response to energization of the driving means for the driven member', housing means for maintaining iluid around and between said lcup-shaped'members, and means cooperating with said cup-shaped members to provide a ltelescopic sliding piston and cylinder relation therebetween including a restricted passage for by-passing the fluid, whereby the u'id confined between said cup-shaped members exerts a dashpot or damping eect for slowing the movement of said upper cup-shaped member into braking engagement with said lower cup-shaped member.

9. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means therefor is deenergized, comprising a pair of upper and lower generally cup-shaped members mounted in opposed coacting relation and having their annular edges provided with cooperating teeth, said lower cup-shaped member being adaptedl to be operatively secured to the driven member forrotation therewith and said upper cup-shaped member being held against substantial rotation and being shiftably mounted for axial up-and-down movement f or eiecting engagement and disengagement between the respective teeth, spring means coacting with said upper cup-shapedfmember for normally urging the latter downwardly into braking v engagement with the lower cup-shaped member, means for retracting said upper cup-shaped member upwardly and out of said braking engagement in response to energization of the driving means for the driven member, housing means for maintaining tluid around and between said cup-shaped members, and a guide bushing mounted in said upper cup-,shaped member and extending coaxially into said lower cup-shaped member to provide a telescopic sliding piston and cylinder relation between said members and including a restricted passage for by-passing the uid, whereby the iluid confined between said cup-shaped members exerts a dashpot or damping effect for slowing the movement of said upper cup-shaped member into braking engagement with said lower cup-shaped member.

10. The structure of claim 9 further characterized in 4that said restricted passage is a predetermined clearance provided between said bushing and said lower cup-shaped member for controlling the displacement of Huid from between said oop-.shaped members during braking `spring `means coacting with said upper cup-shaped member for normally urging .the latter-downwardly into braking engagement with the lower cup-shaped member, means -for retracting said upper cup-shaped member vupwardly and out of said braking engagement in response to energization of the driving means -for the driven memaber, housing means for maintaining a `uid around and between said cup-shaped members, an annular bushing .rigidly held in said upper cup-shaped member and extending coaxially into said lower cup-shaped member, and a circumferential guide lip on said bushing slidably engaging the inner periphery of said lower cup-shaped member for providinga telescopic relation between said .cup-shaped members, said lip having a plurality of ats thereby providing a predetermined clearance between said bushing and said lower cup-shaped member whereby to control the displacement of nid from between said cup-shaped members through said clearance during brak- .ing movement, the fluid confined between said vcup-shaped members .exerting a dashpot or damping effect for slowing the ,movement of said upper cup-shaped member into braking engagement lwith Isaid lower cup-shaped member.

l2. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means therefor is deenergized, comprising a pair of coacting brake members having cooperating teeth, one of which is adapted to be operatively ,connected to the driven member for rotation therewith .and .the other of which is held againstl substantial rotation, one of said brake members also being shiftable into and out of braking engagement with the other of said brake members, means normally urging the shiftable brake memberinto braking engagement with the opposite brake member, and releasing means for disengaging the -shiftable brake member in response to energization of thedriving vmeans for the driven member, said releasing means comprising an actuating ymember having a sliding lost Amotion connection with the Ishiftable brake member and including .an operating portion adapted to engage the shiftable brake member with va delayed impact following said .energization whereby to .overcome any tendency .of the brake members to resist disengagement under load.

'13. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means therefor is deenergized, comprising `a pair of upper and lower generally cup-shaped members mounted in opposed coacting relation and having their annular edges provided with cooperating teeth, lsaid lower cup-shaped member being adapted to be operatively secured to the driven member for rotation therewith, an elongated actuating member having said lupper cup-shaped member slidably mounted thereon and including an enlarged Aportion -at its lower end for engaging and lifting said vupper-sup-.shaped member, means holding Said upper .cup-.shaped member against substantial rotation, spring means coacting with said upper cup-shaped member OI normally urging the latter ydownwardly into braking engagement with vthe lower cup-,shaped member, .and .moans .for axially retraeting said lactuating .member upwardly whereby .to .lift vsaid vHonor Cup-.shaped .member of; said. braking engagement .response to onor-gizetionbt the driving means. tot hs d vaid aotuating member bei g stidable do, said upper Cup-shaped member when said Cup-.shaped members .are in 'braking vengagerrient to position .said enlarged portion in .spaced .relationbelow the ripper oupshapedrmember so that .upon retracting ,of ysaid .actuating member. the enlarged portion thereof engages the upper ycup-.shaped member with :a rdelayed .impact .for overcoming any :tendency toward sticking.

14. The lstructure of claim 13 further characterized `in that said lower cupshaped member .is .affixed to a shaft member extending uirwvardly through the base thereof,

said shaft member being operatively connectible with the driven member, and said venlarged portion at the lower end of said actuating member is operatively supported on the upper end of :said shaft member in spaced :relation below the base portion of the upper .cup-shaped member during braking engagement of said ovp-Shaped membersl5- Brake .means for holding a member rotatably dri-ven in one l.dirootion against, rotation .in the opposite direction when, the driving means therefor is deenergized, .comprising a pair of toothed brake members mounted vin opposed coasting relation, .one `of said brake members being adapted to @be .operatively oonneotod to the driven member for rotation therewith and tho other .of said brake members .be-ing non-,rotatable Vbut shiftable .toward and away .from :the rotatable `brake member fol-.effecting engagement and .disengagement between the toothed portions of -the lrespective brake members, spring means normally urging the shiftable brake member 4into braking engagement with the rotatable Ybrake member, and means for retracting the shiftable brake member from said braking engagementin Vresponse to energization of the driving means for the driven member, each of the :teeth on `.one of said toothed brake members having beveled corner edges for causing axial rebound of the non-rotatable brake member during attempted .engagement of the brake members while the rotatable brake member is ,still rotating .and the toothed portions of the brake members are not in register for braking engagement.

.16. Brake means for holding a member rotatably driven in one direction against rotation in the yopposite direction when the driving means therefor is deenergized, comprising a pair of toothed brake members mounted in opposed coacting relation, one of said brake .members being adapted to be operatively connected to the driven member for rotation therewith and the other of said `brake members being non-rotatable ibut shiftable toward and away Vfrom the rotatable brake member for effecting engagement and disengagement between the toothed portions of the respective brake members, spring -means normally urging the shiftable brake member into braking engagement with the rotatable brake member, and means for retracting the rsh-iftable brake member from -said braking engagement in response to energization of the driving means for the driven mem-ber, each of the teeth on Asaid non-rotatable brake member having beveled corner edges lso Vas to cause axial rebound of the non-rotatable brake member upon impact of said beveled edges against the Acorners ofthe teeth on the rotatable 'brake member during attempted engagement of the brake members while the rotatable -brake member is still rotating and the toothed portions of the brake members are not in register for braking engagement.

1,7. Brake means for holding a member rotatably driven in one direction against rotation in the opposite direction when the driving means therefor is deenergized, comprising a pair of upper and lower generally cupshaped members mounted in opposed coacting .relation and having their annular edges provided with cooperating tooth., .Said lower .oop-shaped member being adapted to be operatively ,secured to .the .driven member .for ro'- tation therewith and said upper cup-shaped member being held against substantial rotation, and being shiftably mounted for axial up-and-down movement for effecting engagement and disengagement between the respective teeth, spring means coacting with said upper cup-shaped member for normally urging the latter downwardly into braking engagement with the lower cup-shaped member, and means for retracting said upper cup-shaped member upwardly and out of said braking engagement in response to energzation of the driving means for the driven member, each of the teeth on said upper cupshaped member having beveled leading and trailing corner edges so as to cause axial rebound of said upper cup-shaped member upon impact of said bevel edges against the corners of the teeth on said lower cup-shaped member during attempted engagement of the cup-shaped members while the lower cup-shaped member is still rotating and the teeth of the respective cup-shaped members are not in register for braking engagement.

References Cited in the tile of this patent UNITED STATES PATENTS 895,152 Bornefeld Aug. 4, 1908 1,206,006 Litfiander Nov. 28, 1916 2,222,419 McCarty Nov. 19, 1940 2,382,870 Gaenssle et al Aug. 14, 1945 2,512,565 Hallander June 20, 1950 2,702,098 Staak Feb. 15, 1955 2,724,474 Hupp Nov. 22, 1955 FOREIGN PATENTS 12,907 Great Britain June 4, 1907

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