Patent Application
20120180587
The present invention relates to load sharing transmissions and, more particularly, to such transmissions assembled from a plurality of modular transmission elements to meet the specific needs of the well being, or to be, pumped.
1. Field of the Invention
The environment in which the present invention has particular, although perhaps not exclusive, utility, is in the area of production of oil and water from wells via a pump, most often a centrifugal pump, driven from the surface by a rotating rod string and speed increasing transmission located down hole (Deep Well Pumping Apparatus, Morris, U.S. Pat. No. 5,573,063.) In particular, the present invention concerns the construction of specialized transmissions built from modules said down hole transmissions.
2. Overview of the Prior Art
The inventor has been intimately engaged on the oil patch for several years and throughout the world and is a recognized expert. He is the holder of several patents in the field of down hole transmissions and particularly multi path load balancing and sharing transmissions, among them Morrow U.S. Pat. No. 5,573,063 relating to a down hole transmission for driving a pump; Morrow U.S. Pat. No. 5,927,147 teaching an early version of a load sharing gear set; Morrow U.S. Pat. No. 6,334,368 relating to a direct drive transmission capable of transmitting large loads relative to its size; Morrow U.S. Pat. No. 6,374,689 relating to a lever system for assisting in the balancing of loads in gear set, and Morrow U.S. Pat. No. 6,619,157 relating to a fluid system for balancing loads on a gear set.
There are additional applications currently pending which bear, generally, on the subject matter of this application. None of these efforts, however, transgress on the novelty of the present invention.
The present invention addresses several needs common to the deep well industry, among them, the ability to adapt a down hole transmission to handle the varying loading needs. Further, it addresses methods of manufacturing and assembly of multi stage modular transmission elements indigenous to a functioning system of load sharing elements.
That said, it is an objective of the present invention to provide the industry with a transmission system which is adaptable to the specific loads which are to be experienced in performing a specific task. Yet another and somewhat more specific objective of the present invention is to provide a down hole transmission which is capable of transmitting significantly greater loads, while maintaining the dimensional parameters required by its environment.
It is a further objective to provide a quantity of substantially identical gear sets as modules which may be readily assembled into a down hole transmission capable of delivering the requisite loads required to drive a down hole pump. By using this type of construction, significant savings can be realized while increasing the capacity of the transmission.
The foregoing, as well as other objects and advantages will occur to those skilled in the art when the following Description of a Preferred Embodiment is read in conjunction with the drawings wherein;
Preliminarily, and as a means of enhancing one's understanding of the principals which define this application, the environment in which the transmission of the present invention has particular, although not exclusive, utility, is below the surface of the earth and as part of a deep well pumping apparatus having an exterior diameter of as little as 4 inches.
The transmission is called upon to drive, e.g., a pump, preferably centrifugal, which is attached to the transmission, from a power source at the earth's surface to several hundred to several thousand feet down a well shaft. The space in which the transmission operates necessarily places severe constraints on the usable loads it can transmit, thus requiring some innovative approach to the problems faced.
A recognized principal feature of the present invention is the ability to stack, or otherwise conjoin, in serial operative relation, like modular gear sets into a unitary load sharing gear train capable of delivering the needed loads to the tool at the end of the drill string.
Morrow (U.S. Pat. No. 5,927,147) has taught the industry various ways that loads may be shared through the use of helical gear pairs and, further, has demonstrated that the capacity of a given gear train can be materially enhanced by adding gear pairs to the gear train. However, it has also been shown that by simply adding gear pairs on an elongated shaft, complications arise which militate against the practical use of such techniques.
It should also be kept in mind that the transmission is an integral part of the apparatus and is, itself, typically several thousand feet below the surface, and if it should fail for any reason, the entire string of production equipment would necessarily be pulled to get at the transmission for repairs or replacement, at an inordinate cost in time and dollars. Reliability, therefore, becomes extremely important, and greatly enhanced construction and assembly is the result. These are just some of the factors which are in play for which the present invention was created.
Turning now to the drawing, and initially to
Size constraints and, in particular, the diameter of the casing in which the transmission must operate, dictate that each gear be rather small, which may be compensated for by increasing the number of gears on a shaft. However, merely stacking gear pairs on a very long drive or driven shaft is somewhere between impractical and ineffective. Primarily, construction of such a gear train adds substantially to cost and difficulty in manufacture. Rather than creating the problems just enumerated, the present invention suggests that by building modular gear trains and connecting them in driving relation, performance can be achieved while problems in construction and manufacture are avoided, or at least minimized.
The present invention contemplates at least two distinct forms of modular gear sets, and, with reference still to
It is essential that intermeshed gear pairs 22 be even in number, in the same ratio, and that those gear pairs be axially aligned, thus substantially identical. Further, alignment must be substantially maintained while the gear pairs are under load, which creates a potential problem due to the tendency of helical gears to move axially under load.
In order to ensure stability and proper alignment when multiple modules are called for, a base plate 26 is provided and mounted thereto are several upstanding bearing blocks 28 which cradle and support the gears via the stub shaft bearing journals, 39, on the ends of each of the gears. With the bearing blocks 28 initially fixed on the base plate, it will be apparent that, as the length of the shafts is increased, the task of aligning the bearing bores for the positioning of bearings in those blocks takes special tooling, and a steady hand is vital and the margin for error slight. The alignment problem is exacerbated by the fact that, in most cases, the base plate and bearing block assembly is so long that the bearing bores must be formed in the bearing blocks before mounting of the blocks to the base plate.
In further keeping with the present invention, problems such as those discussed are capable of being efficiently resolved by employing a modular gear train construction comprised of modules having shorter drive driven shafts and offering uniformity of design, gear ratios and construction and the ability to be interconnected to provide a gear train having the capacity needed for any particular task. Further, each module is short enough so that the bearing bores can be formed while the bearing blocks are affixed to the base plate, allowing great bearing alignment accuracy as required for reliable, long term operation of the transmission.
Referring to
As may be seen there, two gear pairs 22 are provided and joined by a coupler 46. The coupler is formed with an internal spline which engages the tips of the splined tips 42 of the stub shafts 39. As the drive shaft 28 is rotated in a clockwise direction by the power source to which it is coupled in driving engagement, it will be seen that the drive gear tends to move in the direction of the arrow D, causing the driven gear to move in the direction of arrow R.
Thus, a modular gear set 37, in which each gear of a helical gear pair 22 is formed with axial extensions, as distinguished from the drive and driven shafts of
Moving now to
It will be appreciated, as taught by Morrow, that power sharing is created by this arrangement, but in the course of sharing, the gears 24 and 46 will necessarily move laterally as power is applied to the drive gear 24. In order to control the extent of movement of the gears, tension rails 48 are inserted through the central bores 44, along the axis of rotation of the gears, with their termini extending beyond the ends of the stub shafts 39 and retainers 51, e.g., slip rings, although other fasteners may serve the purpose without departure from the invention.
Still referring to
In keeping with the objectives of the invention, the system exemplified in
Applying that understanding, and with reference to
Referring to
It will be appreciated that additional modular units such as unit 37 having two gear pairs may be added to the gear set shown in
The module gear set 20 is but one example of an operative gear set within the contemplation of the invention. With reference to
Referring next to
Reference is next made to
Finally, it will be recalled that the gears, by virtue of their position as engaged on splines, are movable axially in response to the axial forces created by the helical teeth on the gears. While that movement is the genesis of power sharing, the distance moved must be controlled. For that purpose tension rails 48 are centrally disposed in the driving and driven shafts and are of greater length than those shafts. As a result, they protrude beyond the driving and driven shafts and fasteners, such as, e.g., snap rings 79 are fitted on the tension rails to limit gear movement.
Having now described, in considerable detail, an improved multi-stage system for modular transmissions, it is appreciated that those skilled in the art will be able to think of variations on the elements described. Such variations are within the contemplation of the invention as defined by the accompanying claims, wherein:
