US 3656358 A
A collar telescoped over and adapted to be translated back and forth relative to an elongated rod includes cantilevered fingers which are resiliently wedged into angularly spaced grooves formed in the rod to preload the collar onto the rod and to prevent rotational play from developing between the two. In one embodiment, the collar is telescoped onto a rod in the form of a splined shaft while, in another embodiment, the collar is a nut which is threaded onto a screw with multiple threads.
Description (OCR text may contain errors)
United States Patent .Kopp
11 1 3,656,358 [4 1 Apr. 18, 1972  LINEAR POSITIONING DEVICES AN THE LIKE  Inventor: Norman L. Kopp, Beloit, Wis.
 Assignee: Warner Electric Brake & Clutch Compony, South Beloit, Wis.
 Filed: May 19, I970  App]. No.1 38,792
52 us. c1 ..74/s9.15, 74/4248, 74/459, 151/21 R 511 Int. Cl ..F16h 27/02, Fl6h 29/02 58 Field of Search ..74/89.15, 424.8, 424.8 A, 459, 74/841; 151/21 x, 21 A, 21 B  References Cited UNITED STATES PATENTS 2,567,483 9/1951 l-lotine ..74/459 x 3,296,880 1/1967 Maroth ..74/424.8
2,793,538 5/1957 Sears...., ..74/459 1,955,954 4/1934 Dumser ..74/424sx FOREIGN PATENTS 0R APPLlCATlONS 13,628 9/1888 GreatBritain ..151/21B Primary Examiner-Milton Kaufman Assistant Examiner-P. D. Ferguson Attorney-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.
57 ABSTRACT A collar telescoped over and adapted to be translated back and forth relative to an elongated rod includes cantilevered 'fingerswhich are resiliently wedged into angularly spaced 1 grooves formed in the rod to preload the collar onto the rod and to prevent rotational play from developing between the two. In one embodiment, the collar is telescoped onto a rod in the form of a splined shaft while, in another embodiment, the collar is a nut which is threaded onto a screw with multiple threads.
I 8 Claims, 11 Drawing Figures 1 LINEAR POSITIONING DEVICES AND THE LIKE BACKGROUND OF TI-IE INVENTION This invention relates to linear positioning devices and the like of the type .in which a collar is telescoped onto an elongated rod for back and forth translation relative to the latter and is formed with teeth which fit into grooves extending along the rod so as to either key the collar and the rod against relative rotation or to cause one to translate as the other is rotated. For example, the rod either may be a splined shaft or may be a screw adapted for use with a collar in the form of a nut whose teeth constitute a .thread. A positioning device somewhat similar to the present device is disclosed in Sears U. S. Pat. No. 3,364,757.
SUMMARY OF THE'INVENTION The primary aim of the present invention is to provide a positioning device of the above character having a new and improved collar which is especially advantageous for use in conjunction with a comparatively inexpensive rod having multiple grooves and which, at the same time, is preloaded resiliently onto the rod to reduce rotational play between the teeth and the grooves and to automatically take up the play as the teeth and grooves become worn duringnorrnal service use.
In a more detailed sense, the invention resides in the provi sion of a new and improved collar in which at least part of the teeth are in the form of cantilevered fingers which are resiliently urged into wedging engagement with the sidesof the grooves in the rod to maintain a substantially lash-free fit between the teeth and the grooves. One embodiment of the in-.
vention is particularly characterized bythe formation of the fingers and the grooves in the rod on the same helix angle so as to adapt the collar for use with a rod having multiple threads.
These and other objects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspective view of one embodiment of a new and improved positioning device incorporating the novel features of the present invention.
FIGS. 2 and 3 are enlargedcross-sectional views taken substantially along the lines 2-2 and 3-3, respectively, of FIG. 1
FIG. 4 is an enlarged fragmentary cross-section taken sub stantially along the line 4-4 of FIG. I and showing one of the fingers of the collar prior to final assembly of the positioning device.
FIG. 5 is a view similar to FIG. 4 but showing the finger in a deflected position after final assembly of the positioning device.
FIG. 6 is a cross-section somewhat similar toFIG. 4 but showing a modified collar.
FIG. 7 is a fragmentary side elevation of a device with still another type of collar.
FIG. 8 is a fragmentary perspective view of another embodiment of a positioning device incorporating the novel features of the invention.
FIG. 9 is a fragmentary side elevation of still another embodiment of a positioning device.
FIG. 10 is an enlarged fragmentary cross-section taken substantially along the line 10-10 of FIG. '9.
FIG. 11 is a fragmentary perspective view showing the inner side of one of the fingers of the collar illustrated in FIG. 9.
DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the drawings for purposes of illustration, the invention is embodied in a linear positioning device in which an elongated threaded rod or screw 10 is threaded into a collar in the form of a nut 11 such that, upon relative rotation between the two, the nut is translated back and forth relative to the screw. In this particular instance, the nut is clamped rigidly to positioning a movable carriage 13 (FIG. 2) by a strap 14 and moves the carriage back and forth along the screw as the latter is rotated so as to position the carriage along a fixed bed (not shown) which rotatably supports the screw.
Preferably, the screw 10 is of the type having multiple threads, herein five, extending along its length and all formed at the same helix angle by a comparatively simple and inexpensive rolling process. The threads are spaced angularly from one another and are defined by outwardly tapered spiraled teeth 16 (FIG. '2) which are separated by grooves 17 with rounded bottoms. The nut 11 includes a generally cylindrical body 19 made of resiliently yieldable plastic material such as nylon'and' formed with a central internal passage molded with the same number of threads as the screw, the threads of the nut being defined in part by angularly spaced teeth 21 (FIG. 2) which are spiraled at the same helix angle as the teeth 16 of the screw and which fit into the grooves 17 therein. Thus, rotation-of the screw results in engagement of the teeth I6 with the teeth 21 to cause the nut to-translate along the screw and, as a result of the multiple threads formed by the five sets of teeth, load bearing surfaces of relatively large areas are established between the nut and the screw to enable a comparatively small screw to move a heavy load.
In accordance with the present invention, the nut 11, while being especially adapted for use with a multiple threaded screw 10 of the above character, is constructed so as to be capable of being preloaded resiliently onto the screw to reduce rotational backlash betweenthe nut and the screw and to maintain a substantially lash-free condition even as the nut and screw become worn as an incident to normal service use. For these purposes, the nut is formed with a series of cantilevered fingers 25 which constitute part of the threads of the nut and which are resiliently wedged into the grooves 17 of the screw. Thus, full face-to-face contact is established between the fingers 25 and the sides of the screw teeth 16 to minimize rotational play between the nut and the screw and, as the teeth and the fingers wear, such contact is maintained by virtue of the resilient bias urging the fingers into the grooves.
More specifically, the nut 11 herein comprises five fingers 25, one for each of the threads on the screw 10, and each is molded integrally with one end of the body 19 of the nut. The fingers project cantilever fashion from one end of the body and are separated from one another by slots-26 (FIG. 3) extending radially through the nut. This, together with the inherent flexibility of the nylon material of the fingers, enables the fingers to deflect individually relative to the body and inwardly toward the screw, the resistance of the fingers to deflection becoming progressively less along their length toward their free ends. The fingers 25 and the slots 26 are spiraled a partial revolution around the nut at the same helix angle as the teeth 16 and grooves 17 of the screw threads and thus each finger projects into one of the grooves while each slot registers with one of the teeth.
As shown most clearly in FIG. 3, the sides of each finger 25 are tapered inwardly and are sized to fit closely against the sides of the teeth 16 of the screw 10, the inner ends of the fingers being rounded to conform to the shape of the bottoms of the grooves 17. In addition, the inner ends of the slots 26 and the outer ends of the teeth 16 are equal in width so that the teeth may project outwardly into the slots. As a result, the fingers are capable of being wedged into interfitting engagement with the teeth with the adjacent side surfaces of the teeth and the fingers in full face-to-face contact.
When the fingers 25 are in a relaxed condition, their inner ends are spaced a slight distance outwardly from the bottoms of the grooves 17 as shown in FIG. 4.,To wedge the fingers snugly into the grooves, a garter spring 27 fitted in a circumferential groove 29 formed around the free end portions of the fingers contracts the latter inwardly and causes the fingers to deflect relative to the body 19 as shown in FIG. 5. Thus, the fingers are urged resiliently into the grooves and, by virtue of the wedging action, seat against the sides of the screw teeth 16 to substantially eliminate rotational play between the screw 10 and the nut 11 and to maintain the displacement accuracy of the nut for a given increment of rotation of the screw.
From the foregoing, it will be apparent that the present invention brings to the art an anti-backlash nut 11 which is particularly advantageous for use with a multi-threaded screw 10 capable of being manufactured by a simple rolling operation and, in relation to its size, capable of driving heavy loads. The cantilevered fingers 25 are continuously urged inwardly into the grooves 17 by the spring 27 forcing the fingers in the direction of the arrows shown'in FIG. 3 so that, as wear occurs, the fingers are contracted further to automatically take up any looseness between themselves and the teeth 16, such wear decreasing as the fingers gradually seat themselves fully in the grooves during an initial break-in period following installation of the nut on the screw. In spite of wear, the axis of the nut remains substantially centered on the axis of the screw because the fingers are uniformly loaded and tend to wear evenly around the full 360 circumference of the nut. If the load driven by the nut is so heavy as to tend to unwind the spiraled fingers, the loading on the nut shifts to the teeth 21 within the body 19 while the fingers continue to maintain the nut in a preloaded condition on the screw.
A slightly modified nut 11' is shown in FIG. 6 and is adapted to be preloaded onto a screw without need of a separate spring. For this purpose, the inner sides 30 of the fingers 25' are gradually tapered from the body 19' toward the free ends of the fingers so that, in effect, an axially tapered passage 31 is formed between the fingers. When the fingers are relaxed prior to installation of the nut on the screw, the diameter a of the passage near the free ends of the fingers is slightly less than the root diameter b of the screw as shown in full lines in FIG. 6. Thus, as the nut is threaded onto the screw, the fingers are flexed radially outwardly by the screw (as shown in phantom in FIG. 6) and resiliently hug the screw as a result of the resiliency of the nylon material tending to return the fingers to their relaxed positions. Accordingly, the nut shown in FIG. 6 is capable of attaining all of the advantages of that shown in FIGS. 1 to while avoiding the need for a separate spring for contracting the fingers.
Still another nut 40 is shown in FIG. 7 and in this instance, is a double nut formed with sets of fingers 41 and 43 integral with and projecting from opposite ends of an internally threaded body 44. The fingers are preloaded onto the screw by garter springs 45 and, being located at opposite ends of the body, restrict cocking of the body on the screw as well as producing the same friction regardless of the direction of rotation of the screw.
FIG. 8 illustrates another device constructed in accordance with the principles of the invention. In this instance, a nylon collar 50 is telescoped onto a rod in the form of a splined shaft 51 and is adapted to be translated back and forth relative to the shaft and to rotate in unison with the shaft. For example, the collar 50 may be power-rotated to turn the shaft while leaving the latter free for sliding axially through the collar.
The shaft 51 comprises a series of angularly spaced teeth 53 and grooves 54 extending axially along the shaft with zero lead and mating with similarly extending teeth and grooves (not visible) formed within the body 55 of the collar. Integral with and projecting from the collar are cantilevered fingers 56, one for each groove 54, of wedge-shaped cross-section and separated from one another by straight axially extending slots 57. The fingers are contracted by a garter spring 59 and thus are resiliently wedged into the grooves to preload the collar onto the shaft and reduce rotational play between the two.
Another type of positioning device is shown in FIGS. 9 to 11 and comprises a nylon collar or nut 60 having a body 61 which is formed with internal threads like the body 19 of the first embodiment and which is threaded onto a multiple threaded screw 10. Angularly spaced fingers 63 separated by slots 64 project cantilever fashion from the body 61 but, instead of being spiraled in accordance with the screw threads, are straight like the fingers 56 and extend axially along the screw. To provide clearance for the threads of the screw, the inner side of each finger is formed with a series of notches 65 spiraled at the same helix angle as the screw threads and spaced axially along the finger with the same pitch as the screw threads so that the latter mate with and fit into the notches. The notches are formed with an outwardly tapered cross-section and are separated by inwardly tapered teeth 66 which are urged into wedging engagement with the sides of the screw threads by a garter spring 67 contracted around the free end portions of the fingers. The wedging action thus produced takes up play between the nut and the screw. Because the fingers 63 do not follow the helix angle of the screw threads, the nut 60 is in some respects easier to manufacture than the nut 11 of the first embodiment but does not experience as long a life since the notches 65 will eventually bottom against the crests of the screw threads as wear occurs after extended service use.
I claim as my invention:
1. In a positioning device, the combination of, a screw having a plurality of threads all spiraled at the same helix angle, and a plastic nut having a body with the same number of threads as said screw and spiraled at the same helix angle whereby the nut may be threaded onto the screw, said nut including a plurality of angularly spaced spring fingers each extending from said body and each having one end integral with and cantilevered on one end of the body, there being one finger for each thread of said screw with each finger being spiraled at the same angle as the helix angle of the screw threads and making a partial revolution around the screw whereby the fingers mate with the screw threads, said fingers resiliently engaging the threads of said screw to take up rotational lash between the nut and the screw.
2. A positioning device as defined in claim 1 in which said fingers are of wedge-shaped cross-section and are resiliently wedged against the screw threads.
3. A positioning device as defined in claim 2 in which said fingers are separated by angularly spaced slots spiraled at the same helix angle as the fingers and receiving said screw threads.
4. A positioning device as defined in claim 1 further including a garter spring contracted around the free end portions of said fingers and resiliently urging the latter against the screw threads.
5. A positioning device as defined in claim 1 in which fingers define a central passage and are tapered along their inner sides from said body toward their free ends such that the diameter of said passage near the free ends of the fingers is less than the root diameter of said screw prior to threading of said nut onto said screw, said fingers flexing outwardly relative to said body as an incident to the threading of said nut onto said screw.
6. The combination of, an elongated rod with a series of angularly spaced teeth and a series of angularly spaced grooves extending therealong, a plastic collar telescoped onto said rod and adapted to be translated back and forth relative to the rod, said collar including a body and a plurality of angularly spaced spring fingers each extending from said body and each having one end integral with and cantilevered on one end of the body, there being one finger for each groove, said teeth, said grooves and said fingers extending axially along said rod with a zero helix angle and coupling said rod and said collar for rotation in unison and for relative translation, each finger extending along its respective groove along its entire length and being wedged against and resiliently engaging adjacent teeth on said rod to take up rotational lash between said rod and said collar.
7. The combination defined in claim 6 in which said fingers are separated by angularly spaced slots which receive said teeth.
8. The combination defined in claim 6 in which said body is formed with angularly spaced teeth fitted into said grooves in said rod and is formed with angularly spaced grooves receiving the teeth of said rod.