US2435711A - Stroke control for reciprocating pumps - Google Patents

Description

Feb. 10,1948. w. B. CROFTON STRdKE CONTROL FOR RECIPROCATING PUMPS :5 sheets-sheet 2 Filed Dec. 27, 1944 Jfiei B. Cro #01:

w. B. CROFTON STROKE CONTROL FOR RECIPROCATING PUMPS Feb. 10, 1948.

, Filed Dec. 27, 1944 3 Sheets-Sheet} Patented Feb. 10, 1948 STROKE CONTROL FOR RECIPROCATING PUMPS Wilfred Brereton Crofton, Illovo, Johannesburg, Transvaal, Union of South Africa, assignor of one-half to Koppel Engineering (Proprietary) Limited, Johannesburg, Transvaal, Union of South Africa Application December 27, 1944, Serial No. 569.938 In the Union of South Africa January 28, 1944 6 Claims. 1

This invention relates to reciprocating pumps, and in particular to windmill driven vertical lift pumps.

Various means have hitherto been proposed whereby the stroke of the pump may be varied at will. In general, however, these means have not served to vary the stroke automatically in accordance with changes in the power of the Windmill or other power unit. Alternatively, in cases in which the variation in stroke has been effected automatically, the means for doing so has been complicated in construction, expensive to install, and difficult to maintain in efficient operation.

The object of the present invention is to provide a simple and reliable meansfor varying the stroke of the pump automatically according to the power availabl and, to this end, I provide, in accordance with the invention a stroke-varying means which comprises, in combination, a dual transmission arrangement whereby, for a constant stroke of the windmill rod or pitman,

the pump rod or plunger can be operated either with the same stroke as the pitman or a stroke different from that of the pitman, and a combined trip and inertia-mass mechanism whereby it is determined, at the end of each idle stroke of the pitman, whether a power stroke will be transmitted to the pump rod or plunger equal to or difierent from the stroke of the pitman.

Some embodiments of the invention will be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a front elevation of one form of strokevarying means embodying the invention, the trip and inertia-mass mechanism being omitted for the sake of clearness.

Figs. 2, 3 and 4 are respectively a front elevatlon, plan and side elevation, of the said means, illustrating the trip and inertia-mass mechanism.

Figs. 5 and 6 are front elevations of two other forms of stroke-varying means according to the invention, again omitting for clearness the trip and inertia-mass mechanism.

Referring to Figs. 1 to 4 of the drawings:

In the means shown in these figures, the dual transmission arrangement includes a pair of levers I, l which are connected to pivot pins 2 and 2 carried by lugs 3, 3 on the windmill rod or pitman 4. The outer ends of the levers I, l are fulcrumed on pivot pins 5, 5 which are carried by links 6, 6 pivotally connected at I, I to a bracket 8 which rests on the top of the rising main 9 of the pump.

The pump rod or plunger l0 passes up through the bracket 8 and has a cross-head l| fixed thereto by nuts l2. The cross-head H is fitted with guide rods l3 which are slidable vertically with respect to guide sleeves l4 provided on the windmill rod or pitman 4. Links I5, l5 connect the cross-head II to pivots l6, Ili situated at or about the middle of the levers I and l respectively.

The trip and inertia-mass mechanism comprises a cam or ramp (Fig. 3 and 4) welded firmly to one side of the wind mill rod or pitman 4. A pendulum I8 is mounted on a fulcrum pin l9 mounted in an arm 20 provided on the rising main 9 or other fixed part of the pump. The pendulum |B has an upwardly-extending arm 2| fitted at the top end with a roller 22. Alternatively, the ramp may be provided on the top of the arm 2|, and the roller on the pitman 4. A pusher-bar 23 is connected to the pendulum |8 by a pin 24 just below the fulcrum l9. An apertured bracket 25 is fixed on a lever 26 mounted on a fulcrum 21 carried by an arm 28 secured on the rising main 9. An inner nut 29 and an outer nut 3|] are screwed on the end of the pusher bar 23 and a sleeve 25*- is provided on the bar 23 between these nuts to form a replaceable member, whereby the bar will be slidable through the aperture of the bracket 25. An upwardly projecting rod 3| is supported on a compression spring 26 on the top of the lever 26. windmill rod 4, at the side opposite from the ramp H, a transverse bracket 32 is welded. This bracket carries a fulcrum pin 33. A latch 34 is free to pivot about the pin 33, except as limited in an inward or clockwise direction by a fixed stop 33 The windmill rod 4 also has a bifurcated bracket 35 welded thereon, wherein a fulcrum pin 36 is carried, on which is pivoted a vertical or substantially vertical tie-rod 31. A hole 38 is formed in the tie-rod 31 near the bottom thereof. This hole 38 is of a size sufiicient to receive a pin or stud'39 which is formed on a cross-piece 40,.welded in place between the guide rods l3 (Figs. 2 and 4) of the cross-head The tie-rod 31 is provided with a lateral extension 4| which is under the downward constraint of a compressed spring 4'2.

. When the power available to drive the windmill rod or pitman 4 is below a predetermined limit, the ramp will act upon the roller 22 with a force insuflicient to cause the pendulum Hi to On the the top of the rod 23;! will contact the :lateral displace the pusher-bar 23 any further to the right (Fig. 4) than is indicated by the full-line position of the said bar in Fig. 4, i. e. a distance substantially equivalent to the distance at w Leh the inner and outer nuts 29, 3|) are .set apart from each other. The movement of the pusher-bar 23 corresponding to the swinging of the pendulum l8 from the innermost position indicated in dotted lines at |8 to the position shown in full lines in Fig. 4 is thus a lost motion so far as operation of the lever 26 is concerned. Under these conditions of operation, the pump rod ll] remains connected with the windmill rod 4solely through the cross-head links l5, |5 and leuers -1 since therefore the ratio of the leverages about the fulcrum 5 and 5 of the pivots l6, l6 and the pivot pins 2, 2 is only 1:2, the cross-headl1 and P1111 9 rod II] will move with only one half of the length of stroke of the windmill rod 4 (compare the full line and dotted line positions of the lever arrange ment in When, on the other hand, :the cam Dr ramp N (Fig. a) strikes or acts against the roller 22 with a force above the predetermined limit, the pendulum J 8 wi l swi e as de a su fie ntdistanc to a new position 18 (shown by chain-dotted lines in Fig. ,4) to cause the pusher-bar 23 (through its nut 29) to push the lever 26 in a clockwise direction so that the upwardly-projecting rod 3| is moved aside to the right to .a new position figl (-Fig. 4). After a momentary interval, the latch 34 makes contact with the .top of the rod .31, which arrests the downward movementof the latch .34 and causes it .to assume the position 34* shown in dotted lines in .Fig. 4. In this position, the nose of the lateral extension 4| of the tie-rod 31 is released from the latch 34 and the compressed spring 42 presses the extension =4 downwards and forces the tie-rod 3'! to the left (Fig. 4), so that the pin .or stud 39 .provided on the cross-piece 40 will engage in the hole .38. This movement or changewuer takes place when the windmill rod 4 is temporarily at rest at the bottom of its stroke so that nos train, noise or ibration occurs. When this changeover is complete, the windmill rod 4 and pump rod .ID (along with the bracket :8 .and the associated links 6, 6 and -|.5, J5 and levers 1, P) will move in unison duringthe ensuing upwarder power stroke (see Fig. 2 which illustrates the position of the parts .at the -completion of this stroke)- The latch 34:15 mainly sed to prevent wear on the hole .38 and pin 39. At .the bottom .of

thestroke, .the cross-head rests on the bracket 8, so that .the hole and pin engage and disengage without friction.

At the end .of each downward r idle stroke of the Windmill rodor pitman 4,,the cam or ramp acts .upon the pendulum I 8 in the manner referred to and determines, .acconding to .the amount of swing of the pendulum, whether the next upward or power stroke of the pump rod 2'20 will beequivalent only 2110-9, :half of the stroke .of the ,pitman -4 .as transmitted through the aforesaid ,levers i links -|5,, l-5 and .crosshead II, or to the whole stroke ofthe nitman :4, as transmitted through the tie-rod 3.1. If the power available drops below the predetermined limit, the swing ;of the pendulum .|;8 will he 'insufi ei nt to displace the r d 3 wh c will thus occupy the posi i n shown in .iiull nes in R 4 w e the pitman .4 d sc nds.- Consequently. as t e m tman an eaehes t e i-bettompfits stllQlifi,

4 extension 4| and force the tie-rod 31 out of engagement with the pin or stud 39. The bevelled nose of the extension 4| will ride upwards past the bottom 1159 0f the otel; 43 of the latch 34, which will then move under the nose of the extension 4|, and hold the tie-rod 3'! in its disengaged position. The direct connection between the windmill rod 4 and pump rod ID will thus be eliminated, and the windmill rod will continue to drive the pump rod indirectly through the levers I, l links 5, L5 and cross-head. until the power again rises above the predetermined limit.

If desired, means may be provided for varying the position of the link or links towards or away from the fulcrum or fulcrums of the aforesaid lever or levers. In this manner, initial adjustments in the fraction of the pitman stroke transmitted by the links to the pump rod can be effected.

Referring to Figs. 5 and 6:

,In these figures, alternative forms of dual transmission arrangements are illustrated.

In Fig. 5, instead of the indirect or halfestroke transmission being eifected through levers as in the arrangement shown in Fig. 1, it is efiected through a double toothed rack fixed to the windmill rod 4, and through twin toothed pinions .54, 52 which are mounted on plates 53 fixed to the pump rod 10 and which are in mesh with twin racks .54, 5.5. These racks are formed on a rectangular frame 56 through the upper and lower apertures .51 and 5.8 of which .the windmill and pump rods 4 and .ID are slidable, As long .as the indirect or half-stroke transmission continues, the frame .56 restson the top of the rising main .9. Thus, duringthe working .or up strokes, when the double rack .50 rises with the windmill rod 4, the pinions5l, 52 will roll upon the twin racks 54, as a base. Asa result, the plates .53 and pump rod |.0 travel up only half the distance travelled by the windmill rod 4.

The trip and. pendulum .mechanism which is used with the transmission arrangement shown in Fig. 5 is identical with thatalready described with reference to Fig. 4. The pin 39 for engagement with the hole in the tie-rod is formed .on the adjacent plate 5.3 (see Fig. 5). Alternatively, the pin may be provided on the tie-rod and .the hole in the plate.

The transmission arrangement .shown in Fig. .6 is very similar .to that .shown in .Fig. 5. In lieu .of the racks and pinions, two hains 6.0, 1H and pulleys 62., L63 are provided. The .chains are connested to lugs 5.4, .65 on the rectangular frame 5,6 and are led down underneath the pulleys 62, 16,3 and up .to ahead .66 fixed on the lower end of the windmill rod 4. During the half-stroke transmission, .the chains .50, 5|, on each working or up stroke, wil raise .the pulleys 62, ,631onlyone-half stroke. Th s pu a u ted in plates 67 fixed .to .the .top of the pump rod |-0 which thus receives, :under these conditions, only strokes equal :to one-half .of the strokes of the windmill rod 4. The reference numeral .68 indicates the hole (or pin) adapted :to be engaged by the pin .(or hole) .of the tie-rod 31 (Fig. '4) -for;di rect or full stroke operation.

s will be apparent. lth u h. in e n t u t n d scr d n o isiq is made Or transmis- 781011 to .the pumprod of onlyeither the full stroke .of the ritma-n .1 one :Darticular fraction of such stroke, the range (of the overall variation .of the power ratio is very wide since the incidence and number of fractional strokes which are inter- 'PQSfiQ in series with full powerzstrokeswill vary automatically according to the power available at the windmill rod or pitman, from time to time. Thus, each full stroke of the pump rod may be followed by a fractional stroke of the same, or every two consecutive full strokes may be followed by one fractional stroke, and so on.

Various modifications may be made in the means described without departing from the scope of the invention. For example, instead of employing a pendulum as an inertia-mass, I may employ an inertia wheel.

I claim:

1. Means for varying the stroke or reciprocating pumps comprising, in combination with a driving rod and a pump rod, transmission means connected to the driving rod and the pump rod for driving the latter, and inertia means connected to the pump rod and operable by the driving rod in dependence upon the speed and power of the latter to vary or adjust the movement of the pump rod according to the force exerted by said driving rod.

2. Means for varying the stroke of reciprocating pumps comprising, in combination with a driving rod and pump rod, means for directly connecting said driving rod to said pump rod, transmission means adapted to transmit power from said driving rod to said pump rod with a of each idle stroke of said driving rod to adjust the stroke of the pump rod upon a change in the power of the driving rod.

3. Means for varying the stroke of reciprocating pumps comprising, in combination with a driving rod and pump rod, means for connecting said driving rod directly to said pump rod, transmission means adapted to transmit power from said driving rod to said pump rod with a mechanical advantage, an inertia responsive device connected to the pump rod and operable by the driving rod including means whereby said device is set in motion at each idle stroke by said driving-rod, and trip mechanism connected to the driving rod to uncouple the connecting means and to couple together said driving rod and pump rod through said transmission means when said inertia-mass device is acted on with a predetermined force by said driving rod.

4. Stroke-varying means according to claim 1, in which the transmission means comprises a tierod to act as a direct connection between said driving rod and pump rod, and a device is provided as a mechanical advantage in the transmission between said rods.

5. Stroke-varying means according to claim 2, in which said transmission means comprises a lever device.

6. Means for varying the stroke of reciprocating pumps comprising, in combination with a driving rod and pump rod, means for directly connecting said driving rod to said pump rod, transmission means adapted to transmit power from said driving rod to said pump rod with a mechanical advantage, and inertia mechanism connected to the pump rod operable at the end of each idle stroke of said driving rod to adjust the stroke of the pump rod upon a change in the power of the driving rod, said inertia mechanism comprising a cam connected to said driving rod, a tie-rod pivotally secured to said driving rod, an element on said pump rod engageable by said tie-rod, spring means adapted normally to maintain said tie-rod in engagement with said element, and a pendulum projecting into the path of said cam to be acted on by said cam with a predetermined force near the bottom of the stroke to detach said tie-rod from said element and establish a connection between said driving rod and pump rod through said transmission means.

WILFRED BRERETON CROF'ION.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 459,573 Caswell Sept. 15, 1891 841,601 Summers Jan. 15, 1907 1,143,158 Young June 15, 1915 1,498,099 HoWIand-Shearman June 1'7, 1924

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