Power Tool Control

Abstract

A power wrench that has a stationary part and a rotary part and a motor for rotating the latter, also has a switch for shutting off the power of the motor. The switch is actuated by a clutch-controlled arm that determines the degree of rotation of the rotary part after a preliminary tightening so that the degree of final tightening is closely controlled.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns power tools in general, and more specifically, relates to a power wrench of the type that rotates one part relative to another. A particular example is the type of tool that is used in tightening sucker rod joints. The common name for such a tool as employed in oil field operations, is "power tongs."

2. Description of the Prior Art

Heretofore it has been found that problems arise in making up sucker rod strings by reason of having the joints put together either too tight which causes failure, or too loose which permits disengagement. In either case the results can be quite expensive in time and equipment because of the resultant difficulties or loss of equipment.

Consequently, it is an object of this invention to provide a power wrench that can tighten a shoulder butt joint automatically for a predetermined degree of turning after a so-called hand-tight joint as been effected.

SUMMARY OF THE INVENTION

Briefly, the invention concerns an improvement that is in combination with a power tool. Such power tool has a stationary part, a rotary part, and a motor for rotating said rotary part relative to said stationary part. The tool includes means for supplying power to said motor as well as a switch for terminating application of said power. The improvement comprises means for actuating said switch after a predetermined amount of rotation of said rotary part, and such means comprises first means for measuring the amplitude of force being applied by said motor, and second means for measuring the amount of rotation of said rotary part commencing with a predetermined amplitude of said force being applied by said motor.

Again, briefly, the invention relates to a combination with a power wrench which has a stationary part, a rotary part and power means for driving said rotary part in rotation relative to said stationary part. It is also in combination with means for tightening a shoulder butt joint a predetermined fixed amount. The combination comprises switch means for releasing application of said power means, and means for driving said rotary part until said shoulder butt joint has made contact. It also comprises means for actuating said switch means after a predetermined degree of rotation of said rotary part, following said butt-joint contact.

Once more, briefly, the invention concerns the combination with a fluid motor powered rotary tool having a rotating part and a stationary part. The tool also comprises means for automatically driving said rotating part for a predetermined degree of rotation after a predetermined amplitude of force has been reached. The combination also comprises a switch for shutting off said fluid motor, and said switch has an actuator therefor. The combination also comprises a shaft having an enlarged rotor on one end thereof and being shiftable longitudinally for placing said rotor into contact with said rotating part. It also comprises a diaphragm attached to the other end of said shaft for shifting same when fluid pressure is applied, and a spring for urging said shaft against the force applied by said diaphragm. The said spring has sufficient strength to permit preliminary rotation of said rotating part without shifting said shaft. It also comprises a radial arm carried by said shaft and adapted for contacting said switch actuator after a predetermined degree of rotation of said shaft when shifted so that said rotor is in contact with said rotating part, and a return spring for biasing said shaft in rotation to a starting position prior to said rotation when the rotor is in contact with said rotating part. It also comprises means for adjusting said starting position in order to predetermine the degree of rotation of said power tool after said amplitude of force has been reached.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and benefits of the invention will be more fully set forth below in connection with the best mode contemplated by the inventor of carrying out the invention, and in connection with which there are illustrations provided in the drawings, wherein:

FIG. 1 is a plan view of a power tool that includes the invention therewith;

FIG. 2 is a side elevation of the tool illustrated in FIG. 1, partly broken away in cross-section;

FIG. 3 is an enlarged fragmentary cross-section, showing some of the principal elements of the invention as related to the tool shown in FIGS. 1 and 2;

FIG. 4 is a fragmentary enlarged plan view of the invention as shown in FIG. 3;

FIG. 5 is another enlarged fragmentary cross-section view like FIG. 3, but showing the parts in a shifted position after a given pressure has been applied; and

FIG. 6 is a fragmentary enlarged plan view like FIG. 4, but showing the parts in the final position as a switch for cutting off power is being actuated.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, it is pointed out that this invention may be applied to conventional power tongs of the type illustrated. Such power tongs are well known in oil field operations and, in the particular application of this invention, the tool is being applied to tightening the joints of a sucker rod string (not shown). However, it will be appreciated that the invention may be applied equally to other power tools, and particularly those tools where the joints to be tightened are the butt-joint type. Those skilled in the mechanical arts generally will appreciate that, in shoulder-butt joint connections, the first threading action will require very little power until the shoulders of the joint have come in contact. The shoulder contact position is often referred to as a hand-tight joint, since the first threading may be carried out manually. Thereafter, when this invention is employed, the joint may be tightened automatically for a predetermined degree of rotation exactly. In this manner, a string of sucker rods, for example, can be made up with a consistent and exact tightness at every joint which will prevent either failure from overstressed joints or uncoupling from having a joint too loosely made up.

The power tool illustrated in FIGS. 1 and 2 may be pneumatic or hydraulic. It includes a motor 11 that has a pair of hose couplings 12 and 13 that are connected as generally indicated, for introducing the flow of power fluid. Energization of the motor is controlled by a valve 16 which has a control lever 17 (FIG. 2). In addition, it is to be particularly noted that although it is not shown, there would be an actuator that is under control of a switch 18. It will be understood that switch 18 might be a fluid relay, or an electrical switch if the valve 16 should be controlled electrically. In either event actuation of valve 16 would be carried out under the control of the switch 18 by any feasible arrangement (not shown) which depends on whether switch 18 were electrical or fluid type, i.e., pneumatic or hydraulic. Thus, it will be clear to one skilled in the art that conventional equipment (not shown) would be employed to permit the switch 18 to control actuation of the valve 16 to cut off power to the motor 11 when the switch is operated.

The illustrated power tool is largely conventional. As will be apparent, it has what may be termed a stationary part, i.e., the housing 19, in general. There is attached to the housing 19 (underneath as viewed in FIG. 1) an arm 21 that has end wrench jaws 22 at the extremity thereof. These jaws 22 will engage the flat sides of the lower joint (not shown) of a sucker rod string (not shown) that is being made up. The wrench jaws 22 will hold the lower joint stationary against rotation while an upper joint (not shown) is threaded into the lower. Rotation of the upper joint is carried out by a ring gear 25 (FIG. 2) that has attached thereto concentrically an inner ring element 26 which is designed to support a pair of pivotally mounted jaws (not shown) that are designed to engage the square-sided portion of the upper joint of the sucker rod string. It may be noted that the ring gear 25 has an opening in alignment with the opening in ring element 26. This is to permit the upper sucker rod joint to be placed into the tool at the beginning of a tightening operation, through a pair of pivoted jaws 27 and 28.

Power for rotating the ring gear 25 comes from the motor 11 via a gear train, as shown, which includes a pair of idler gears 29 and 30 that mesh with ring gear 25. Next, there is a pinion 33 that is formed on the upper extension of a gear 34 (FIG. 2) that is in the train of gears from the motor 11. The gear train includes a compound gear 35 (FIG. 2) that is driven directly by a pinion (not shown), which is carried on the shaft of the motor 11.

It should be understood that the usual operation of the power tool so far described, is straightforward and well known. Control of motor 11 could be manual, i.e., by means of the lever 17 which controls valve 16. However, there is usually a pressure switch (not shown) that controls the amount of torque applied. But it does not give accurate makeup or satisfactory results since some 80 to 90 percent of the applied torque is necessary to overcome friction in the joint. On the other hand, by use of this invention a shoulder-butt joint may be made up and will automatically be tightened for a predetermined degree of rotation after the joint has become "hand-tight" by cutting off the application of power at that point.

In order to accomplish the foregoing, there is structure in accordance with this invention including a clutch-like arrangement to automatically operate the switch 18 after the foregoing degree of rotation has taken place. It will be appreciated that various other structures for carrying out the invention might be employed without departing from the principles involved. Thus, it will be understood that the particular elements illustrated are schematic and the dimensions or particular arrangement might be varied. For example, it would probably be more practical to reverse the relative sizes of the diameters of rotors 42 and 45, which will be described in more detail below.

There is a shaft 41 that carries the idler gear 29. This shaft 41 has an enlarged rotor 42 at the extremity thereof. Rotor 42 has the switch 18 located adjacent thereto in order to provide desired clutching action, as will apear below. There is a rotor 45 that is attached to the end of a shaft 46 (FIGS. 3 and 5) which shaft is attached at the other end thereof to the center of a diaphragm which divides a cavity 50 in half.

The shaft 46 and rotor 45 are secured together in a fixed manner so that no relative rotation can take place between them. But the shaft 46 is rotatable by being mounted in any feasible manner to permit it. However, the rotation is restrained by a coil spring 53 which urges the shaft 46 in clockwise rotation (when viewed as shown in FIGS. 4 and 6) so as to hold a radial arm 54 which extends from the rotor 45, to be in contact with a stop 55 so long as the rotor 45 is not rotated against the spring action.

It will be observed that the spring 53 acts in conjunction with a collar 56 (FIGS. 3 and 5) that is keyed to the shaft 46 with a sliding fit so that the shaft may slide vertically (as viewed in the drawings) while being held for no relative rotation with respect to the collar 56. Also, it will be noted that when the two rotors 42 and 45 are in contact with one another, the arm 54 which extends radially from the upper hub portion of rotor 45, will be rotated in an arc counterclockwise (as viewed in FIGS. 4 and 6) and in the same plane as an actuating arm, or lever, 58 of the switch 18.

It will be observed that the lower portion (as viewed in the drawings) of the cavity 50 is connected by passageways 59 and a pipe 60 (FIG. 2) to a fluid pressure meter 63 (FIG. 2) that indicates the amplitude of the fluid pressure that is being applied to the motor 11. The meter 63 is, of course, also connected by internal passages, etc., (not shown) to the motor 11 in such a way that the effective load on the motor will be indicated by the pressure reading and which same pressure is being applied to the diaphragm 49 on the underside. This pressure will act against the force of a spring 67, to be described hereafter.

In the upper part of the cavity 50, there is a recess 66 which accommodates the coil spring 67 that surrounds the shaft 46 and bears against the collar 68. Collar 68 is carried by the shaft 46 and holds the spring 67 in compression because the other end of the spring 67 bears against the end wall of the recess 66. Consequently, the spring 67 urges displacement of the shaft 46 and its attached rotor 45, along with the flexible diaphragm 49, downward (as viewed in the drawings) toward the position illustrated in FIG. 3.

On the other hand, when sufficient fluid pressure is applied to the lower portion of cavity 50, beneath the diaphragm 49 (via passageway 59 and pipe 60), it will lift the shaft 46 against the force of spring 67 and bring the rotor 45 into contact with the other rotor 42. In this manner, after the preliminary tightening of a joint has taken place, the pressure of power fluid to the motor 11 will increase and become sufficient to cause the foregoing clutching action for engaging the rotors so that after the arm 54 has been swung around from its at-rest position, it will come in contact with the actuating arm 58 of the switch 18. Then the actuation of switch 18 will cut off the power to motor 11 and the tightening of the joint will be completed. It will have automatically been tightened with a predetermined fixed degree of rotation.

It will be appreciated that the degree of rotation is controllable and may be set for a predetermined amount that may be adjustable by having different sized stops 55 for holding the arm 54 in its starting or at-rest position.

OPERATION

In order to help clarify the invention, it may be noted that operation of the illustrated embodiment is as follows:

Beginning with the situation where a joint (not shown) to be tightened is placed in the tool, the upper end of a sucker rod or other member having a shoulder butt or other butt-type threaded coupler, will be placed into the jaws of the end wrench 22. The lower end of another sucker rod or other member to be attached to the first will be placed into jaws (not shown) carried by the ring element 26. Then, after the threads of the couplers have been started, the first step will be application of fluid power to the motor 11, so as to cause preliminary rotation of the upper half of the joint. During this preliminary action, there will be very little resistance to the tightening rotation, and the pressure reading from the motor 11 will be much less than that required to force the diaphragm 49 to raise the shaft 46 against the spring pressure of spring 67. Consequently, as the upper rod is being rotated during such preliminary tightening, the rotor 42 will, of course, be rotated, but without any contact thereagainst by the declutched rotor 45. Consequently, this preliminary rotation may vary to almost any extent, e.g., for many complete revolutions as the threads are being started, without affecting the operation of the final tightening action.

In order to control the degree of final tightening for a predetermined amount of rotation after the shoulders of the butt joint have come in contact, it is the increase in pressure of the fluid as applied to the motor 11 that will be sufficient to overcome the spring pressure of spring 67. This will raise shaft 46 and place rotor 45 into contact with rotor 42, as shown in FIG. 5. As soon as these rotors make contact, it will cause rotor 45 to be rotated along with the radial arm 54 (now raised up into the same plane as the switch arm 58) against the spring action of the spring 53. Such rotation will continue, along with the tightening action of the tool, until the radial arm 54 contacts switch actuator 58. The actuation of switch 18 will control the cut-off of power to the motor 11 and, consequently, stop further rotation of the tool. This will then have caused a given degree of rotation of the joint beyond the condition of abutment of the shoulder butt elements, and this rotation will have been closely controlled for a predetermined degree of rotation.

After the power has been cut off, the pressure is concomitamtly reduced and, consequently, the spring 67 will return the diaphragm 49, along with the other elements carried by the shaft, to the lowermost position, as illustrated in FIG. 3. When the rotor 45 no longer contacts the other rotor 42, shaft 46 and the elements attached to it will be free to rotate. Then the spring 53 will return arm 54 back to its starting position in contact with stop 55, as illustrated in FIG. 4. Thereafter, the tool will be ready to carry out another tightening operation.

As mentioned above, it will be appreciated that particular design features including dimensional aspects of the elements relating to automatic rotation control according to this invention, might vary considerably from that illustrated in the drawings without departing from the principles of the invention. For example, it may be impractible to employ a rotor 42 with as large a relative diameter as that indicated in the drawings. Thus, the showing is made with a view to setting forth clearly only the principles of the invention. Also, as indicated, the details of controlling power cut-off by means of the switch 18 have not been shown. These could take various forms within the purview of one skilled in the art.

It will also be appreciated that the directions of threads at a joint being automatically tightened by the tool, might be reversed. In such case the arrangement of the parts relating to the clutch and actuator for control switch 18 would also be reversed to accommodate the opposite rotation involved.

While a particular embodiment of the invention has been described in considerable detail above, this is not to be taken as in any way limiting the invention, but merely as being descriptive thereof.

Claims

What I claim is:

1. In combination with a power tool having a stationary part, a rotary part and a motor for rotating said rotary part relative to said stationary part, including means for supplying power to said motor and a switch for terminating application of said power, the improvement comprising:

means for actuating said switch after a predetermined amount of rotation of said rotary part following a substantial and sudden increase in force applied, comprising

first means for measuring the amplitude of force being applied by said motor comprising clutch means having a shaft with a rotatable member attached thereto, and means for displacing said shaft longitudinally, and means for biasing said clutch means to a disengaged state unless said amplitude of force exceeds a predetermined amount,

second means for measuring the amount of rotation of said rotary part commencing with a predetermined amplitude of said force being applied by said motor, comprising means actuated by said clutch means when engaged, including means actuated by said rotatable member when said shaft is displaced for actuating said switch.

2. The invention according to claim 1, wherein said shaft-displacing means is a diaphragm, said biasing means is a spring, and said means actuated by said rotatable member comprises

a rotor attached to said shaft for contacting said rotatable member, and

a radial arm extending from said shaft for actuating said switch.

3. The invention according to claim 2, further including

a return spring for said shaft to bias it into a starting rotary position, and

means for adjusting said starting rotary position.

4. In combination with a power wrench having a stationary part, a rotary part, and power means for driving said rotary part in rotation relative to said stationary part,

means for tightening a shoulder butt joint a predetermined fixed amount, comprising

switch means for releasing application of said power means,

means for driving said rotary part until said shoulder butt joint has made contact,

a rotor adapted for being coupled and uncoupled with said rotary part,

a plunger for actuating said rotor from uncoupled to coupled position,

means for biasing said plunger to uncouple said rotor until said butt joint contact, and

an arm actuated by said rotor for contacting said switch after a predetermined amount of rotation of said rotary part.

5. The invention according to claim 4, wherein said switch-actuating means further comprises

a spring for returning said arm to a starting position, and

means for setting said starting position for adjusting the amount of rotation of said rotary part.

6. In combination with a fluid motor powered rotary tool having a rotating part and a stationary part,

means for automatically driving said rotating part for a predetermined degree of rotation after a predetermined amplitude of force has been reacted, comprising in combination

a switch for shutting off said fluid motor,

said switch having an actuator therefor,

a shaft having an enlarged rotor on one end thereof and being shiftable longitudinally for placing said rotor into contact with said tool-rotating part,

a diaphragm attached to the other end of said shaft for shifting same when fluid pressure is applied,

a spring for urging said shaft against the force applied by said diaphragm,

said spring having sufficient strength to permit preliminary rotation of said tool-rotating part without shifting said shaft,

a radial arm carried by said shaft and adapted for contacting said switch actuator after a predetermined degree of rotation of said shaft when shifted so that said rotor is in contact with said tool-rotating part,

a return spring for biasing said shaft in rotation to a starting position prior to said rotation when the rotor is in contact with said tool-rotating part, and

means for adjusting said starting position in order to predetermine the degree of rotation of said power tool after said amplitude of force has been reacted.