WO1995014842A1

WO1995014842A1 - Friction hinge with detent

Info

Publication number: WO1995014842A1
Application number: PCT/US1994/012476
Authority: WO
Inventors: Edward T. Rude; Mikhail Gelfand; David A. Carpenter
Original assignee: General Clutch Corporation
Priority date: 1993-11-24
Filing date: 1994-10-27
Publication date: 1995-06-01
Also published as: AU8129294A

Abstract

An inventive friction hinge (5) is provided which also provides detenting in a position or arcuate range. The friction torque is provided by a spring band (13, 65 or 73) which fits tightly about a shaft (11, 61 or 67) or within the cavity of a housing. Detenting is provided by features (21, 63 or 71) on the band and the mating part (19, 59 or 69) that cause the band to change shape when the features align. The detenting torque can be varied by changing the detailed shape of the features. Covers (3) that close, as on laptop computers, can be held shut by the use of the inventive detenting friction hinge which can also provide the friction needed to hold the screen of the computer in position during operation.

Description

FRICTION HINGE WITH DETENT

This invention relates to hinges and, more particular¬ ly, to hinges in which a controlled amount of friction is intentionally provided between the rotating elements of the hinge. Friction hinges are used to rotatably connect two elements whose relative angular orientation is to be easily adjustable while remaining constant between adjustments- Still further, this invention relates to hinges having a detent in addition to their frictional characteristics. The screens of notebook computers is a common applica¬ tion for friction hinges, wherein it is desirable to set the position of the screen for comfortable and clear viewing. Because these computers must be small and light, battery capacity is at a premium. The limited availability of power means that the brightness and satisfactory viewing angle of the display is often limited, and it becomes very important for the viewer to be able to accurately position the screen and have it remain in that position. Once put in the de¬ sired position, the screen should remain stably at that angle without exhibiting "spring back" as it is released. Additionally, once positioned, the screen should not bounce freely or move without an external tor ue applied by the user. Such slight freedom of movement without resistance is called backlash. Backlash can be quite annoying when there is slight movement of the computer as would occur on a train or airplane.

Weight, size, and cost are all very important factors in .the design of small portable computers, and all of these factors are favorably effected by the elimination of unnec- essary components. Friction hinges are used to mount the display and cover to the computer case, and conventionally, a latch has been provided to hold the cover closed when the computer is moved from place to place. The detenting char¬ acteristics of our inventive friction hinge permits the latch to be eliminated, saving both weight and cost. BRIEF DESCRIPTION OF THE INVENTION

Our inventive friction hinge is based on the well known technology of friction brakes based on the use of wrap springs. However, we have been able to provide a detent while retaining the frictional properties of the friction brake. This friction hinge uses a circular band which fits tightly about a circular shaft. The friction derives from the force required to rotate the band in relation to the shaft. The shaft is attached to one of the parts to be hinged, and one end of the band is attached firmly to the other part to be hinged. In many cases, several bands are employed to achieve the desired frictional characteristics for the hinge. Often, the bands are mounted within a hous¬ ing or are clamped to a flange or bracket in order to pro- vide firm mounting. As will be familiar to those experi¬ enced in the art of wrap spring devices, the frictional torque required to rotate such a band about a shaft is different for the direction of rotation that tends to tight¬ en the band about the shaft than it is for the opposite direction that tends to loosen the grip of the band on the shaft. This directional difference in torque can be advan¬ tageously employed in some situations. Where the applica¬ tion demands the same torque in each direction, an even number of identical bands can be used, half of them wrapped in each direction about the shaft. And, of course, it will be obvious that other clockwise-counterclockwise torque ratios can be achieved by using a number of bands with uneven numbers facing in the two directions.

In the preferred embodiment of our invention, detenting is accomplished by the combination of a non-circular shaft and a similarly shaped spring band which fits over the shaft. As the shaft and band are rotated relative to one another, the band must expand to accommodate the irregular shape of the shaft within it. This results in a restoring torque that opposes the relative motion. For angles near the starting position, the detailed shape of the irregulari¬ ty, and therefore, the rate at which the band must expand, determines the amount of restoring torque that results.

After a certain rotational angle has been traversed, the irregular feature contacts only the circular portion of the shaft. Thereafter, continued rotation in the same direction requires no further change in the shape of the band, and the torque needed to produce relative rotation is due only to the friction between the band and the shaft. Other embodiments of our inventive detenting frictional hinge have a wide range of detenting characteristics. The unique combination of controllable, frictional torque and rotational torque produced by the rotation of one irregular shape within another can be usefully employed in many me- chanical applications, including couplings for machinery, cabinet doors, screen doors, automotive doors, truck lids and hoods, luggage, toilet seats, and kitchen appliances.

It is an objective of our invention to provide a fric¬ tion hinge with reliable and consistent frictional charac- teristics and with a detent at a discrete angular orienta¬ tion.

It is another objective of our invention to provide a friction hinge for a box lid that will remain closed without the need for a separate latching mechanism. Other objects and advantages of our invention will become apparent from the descriptions that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

Further understanding of our invention will become apparent upon consideration of the following detailed de¬ scription in conjunction with the drawings, in which: FIG. 1 is a perspective view of a notebook computer in which one corner of the cover has been cut away to reveal one of the inventive hinges;

FIG. 2 is a partially exploded view of a hinge of the type used in the computer of FIG. 1. FIG. 3 is the same view as FIG. 2 but with the shaft and band in position within one side of the housing.

FIG. 4 is a cutaway view of the hinge of FIGS. 1-3 shown with the shaft in a starting orientation.

FIG. 5 is a cutaway view of the same hinge with the shaft further rotated.

FIG. 6 is like the view of FIG. 5 but with the shaft still rotated still further.

FIG. 7 is an embodiment of our hinge much like the one shown in FIGS. 1-6 but with the addition of a second band. FIG. 8 is another embodiment of our invention in the form of a butt hinge shown in the closed position.

FIG. 9 depicts the butt hinge of FIG. 8 in a slightly open position.

FIG. 10 shows the butt hinge of FIGS. 8 and 9 opened to 120 degrees.

FIG. 11 shows the butt hinge of FIGS. 8 in the closed position, but with the fixed plate removed.

FIG. 12 is an end view of the parts shown in FIG. 11. FIG. 13 is the same view as that of FIG. 12 but with the hinge opened slightly as it is in FIG. 9.

FIG. 14 is the same view as FIGS. 12 and 13, but with the hinge opened to 120 degrees.

FIG. 15 is a partial end view of yet another embodiment of our invention in which the detent has different torque characteristics. FIG. 16 shows the same parts as does FIG. 15, but with the shaft rotated to a different position.

FIG. 17 is a partial end view of a further embodiment which shows another means of achieving the detenting torque. FIG. 18 shows the same parts shown in FIG 17 with the shaft in a rotated position

DETAILED DESCRIPTION OF THE DRAWINGS

The laptop or notebook computer depicted in FIG. 1 is typical of the applications for the hinge of our invention. Base 1 contains the keyboard, battery, disc drives, connec¬ tors, and much of the electronics. Cover 3 contains the display and may also contain some of its associated circuit¬ ry. Friction hinge 5, which would usually be one of two such hinges used, is mounted to the cover by screws 7. Shaft 9 protrudes from friction hinge 5 and is fastened to base 1 of the computer by any suitable means that will provide a non-compliant mounting. The mounting of both the body and the shaft of a friction hinge should be carefully designed to prevent flexing of the base and cover. Any flexing of the parts to which the hinges are mounted will produce springback which detracts from satisfactory opera¬ tion and the perception of quality. An unlimited variety of physical configurations of the hinge and the shaft connec¬ tions are possible, and it is important to select ones that permit the friction hinge to be firmly mounted to surfaces that will flex very little.

One type of friction hinge construction is shown in FIGS. 2, 3, and 4. This is the same general construction as in hinge 5, except that the hinge of FIGS. 2-4 would be for use on the right side of the computer of FIG.l. FIG. 2 shows shaft 11 with band 13 in position about the shaft. Band 13 is made of a spring material that is capable of some deformation without yielding. Lower housing 15 and upper housing 17 are shown as well. Flat 19 extends along a portion of one side of shaft 11. Shaft 11 also has flat 20 for attachment. As a convenience for explanation, Flat 20 has been shown parallel to flat 19, but this is not a re- quirement. In actual practice, the orientation of flat 20 with respect to flat 19 might vary according to the require¬ ments of a particular installation. Band 13 has flat por¬ tion 21 which is shown in contact with flat 19 of shaft 11. Furthermore, band 13 has tail 23 by means of which it is kept irrotationally positioned in the hinge during opera¬ tion. Lower housing 15 and upper housing 17 have surfaces 25 to provide bearings for shaft 11 as it rotates in assem¬ bled the housing.

FIG. 3 shows the same hinge configuration as does FIG. 2, but with shaft 11 in place in lower housing 15. Upper housing 17 is then positioned so that lower housing pins 27, 29, and 31 pass through holes 33, 35, and 37 in the upper housing. The assembly is completed by peening over the ends of posts 27, 29, and 31 to hold the assembly together. As housing halves 15 and 17 are pressed together a narrow rail of material (not shown) presses against tail 23 of band 13 to grip it firmly within the housing. The rail is designed to undergo some deformation during assembly to assure good gripping of the band. FIG. 4-6 show an assembled hinge with one side partial¬ ly cut away so that flat 19 on shaft 11 is visible in rela¬ tion to flat portion 21 of band 13 as shaft 11 is rotated within the housing. In a typical installation, the hinge is mounted in a computer case with flat 20 fastened to the cover of the case. Then the orientation is as shown in FIG. 4, with shaft 11 partially rotated, and flat portion 21 of band 13 applying pressure against the edge of flat 19 of shaft 11 so as to produce a torque that tends to hold the cover against the computer base. This eliminates the need for a separate latch mechanism.

FIGS. 5 and 6 show the orientation of the parts as the cover is opened, and shaft 11 is further rotated. In FIG. 5, flat 19 is further rotated away from flat 21 of band 13. In FIG. 6, shaft 11 has rotated far enough so that there is no further contact between flat 21 of band 13 and flat 19 of shaft 11. Therefore there is no further change in the shape of band 13 as shaft 11 continues to rotate and there is no further torque due to the detenting effect. There continues to be frictional resistance to rotation of shaft 11 within band 13. This friction is controlled by the force exerted by band 13 against shaft 11, by the frictional properties of the surfaces of these two components acting against one another, and by the effects of lubricants that are contained within the hinge.

When the cover of the computer is again closed, the holding torque is applied as before, holding the lid shut.

FIG. 7 shows an embodiment similar to the embodiment of FIGS. 1-6, but with two bands, 39 and 41. If the two bands are identical, then the torque and friction they produce during rotation of the shaft will be double that of the hinge with a single band. Upper and lower housings 15 and 17 of FIGS. 1-6 are shown with space for a number of bands, or conceivably, for one wide band. Various advantages can be obtained by the use of multiple bands. The precise shape of the band is easier to control in manufacturing if it is not too wide. And, in meeting the differing requirements of various customers, it is convenient to be able to assemble a hinge with different numbers of bands to achieve different torque characteristics. By using band materials of various thicknesses, it is possible to obtain a still wider varia- tion in torque characteristics while still using the same housing and shaft parts.

The detenting characteristics of our invention can be incorporated into the very common butt style of hinge shown in FIGS. 8-14. FIG. 8 shows the butt hinge fully closed. FIG. 9 shows the same hinge slightly opened and FIG. 10 shows in opened to 120 degrees. The hinge consists of only four component parts, each visible in FIGS. 8, 9, and 10. Fixed plate 43 is irrotata- bly connected to shaft 45 by pin 47 which extends through the shaft and the fixed plate which wraps around it. Deten- ting plate 49 works in conjunction with shaft 45 to produce both the detenting effect and the frictional effect. As in the earlier embodiments, detenting plate 49 must be made of a material capable of the required deformation without yielding, and of course, the stress must be low enough so that repeated cycling of the hinge will not cause failure. The methods employed to properly account for these factors will be very familiar to those with expertise in spring design.

FIG. 11 shows the hinge without fixed plate 43, to provide a clearer view of detenting plate 49 and shaft 45. Like shaft 11 of the earlier embodiment, shaft 45 has flat 51. Also, like the bands of the earlier embodiments, de¬ tenting plate 49 has a band portion 53 that is wrapped about shaft 45 and has a flat section 55. As best seen in FIG. 12, when the butt hinge is in the closed position, edge 57 of flat 51 is the only part of flat 51 that is in contact with flat section 55 of band portion 53. Since band portion 53 is a spring, it exerts a torque on shaft 45 that tends to further close the butt hinge. FIG. 13 shows the position of shaft 45 when the hinge has been opened slightly, as in FIG. 9. In this position, there is still a torque that tends to drive the shaft into the closed position. FIG. 14 shows the same hinge, opened to 120 degrees, as in FIG. 10, in which position there is no further detenting force. The frictional force resulting from the pressure of band portion 53 on shaft 45 remains, and continued opening of the hinge requires that this fric¬ tional force be overcome.

As a matter of convenience, flat 51 is shown extending the full length of shaft 45, but the portion of the flat that is, in the fully assembled hinge, surrounded by fixed plate 43 is not necessary since the shaft does not rotate with respect to that plate. It is purely matter of manufac¬ turing choice whether to produce the flat for the full length of the pin or only where it is needed for interaction with the detenting feature of detenting plate 49.

The detents of the several embodiments shown above have been configured so that each hinge will hold together the two parts connected to it. But many other configurations are possible. By orienting the detenting features differ- ently with respect to the closed positions, it is an easy matter to provide detenting in any other angular position. Furthermore, different shapes are possible that will provide other detenting characteristics. For instance, a more positive detent, that is, one that provides higher torque to overcome the detenting action, is provided with the shaft and band geometry shown in FIGS. 15 and 16. The shape of detent 59 in shaft 61 is curved as is matching feature 63 of band 65. The torque required to rotate shaft 61 with respect to band 65 will be greater than would be the case if the detenting features on the band and shaft were flats, as in the earlier embodiments. Other characteristics being the same, the torque required to escape the detent position will depend upon the angular rate at which the band must expand. The embodiment shown in FIGS. 17 and 18 provide another means of achieving the same characteristics. Shaft 67 has ridge 69 shaped and sized to fit within hole 71 in band 73. The detailed shape of ridge 69 will determine the torque characteristics of the detent. For instance, if ridge 69 is narrower than hole 71, the torque will remain essentially constant while ridge 69 is rotated from one side of hole 71 to the other, while the torque will be larger when the ridge 69 is completely out of hole 71. By varying the size of hole 71 and ridge 69, this torque characteristic can be extended over a larger portion of the rotational travel of shaft 67. The same operational characteristics can also be achieved by placing a band within a cavity that is slightly smaller than the free size of the band. Then, adding a detent shape to both the band and the housing, the benefits of the detenting hinge of our invention can be achieved. It will thus be seen that the objects set forth above among those made apparent from the preceding descrip¬ tion, are efficiently attained and, since certain changes may be made in the construction of the inventive spring clutch without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are intended to cover all of the generic and specific fea¬ tures of the invention herein described and all statements of the scope of the invention which, as a matter of lan¬ guage, might be said to fall therebetween.

Claims

1. A friction hinge assembly comprising: a shaft comprising a substantially cylindrical member; at least one substantially annular band rotatably fitted about said shaft; wherein said shaft includes means for enabling camming of said at least one band when one of said shaft and said at least one band is rotated about the other in order to selec¬ tively tighten said at least one band about said shaft.

2. The friction hinge assembly of Claim 1, wherein said camming enabling means comprises a depression formed along a portion of said cylindrical member.

3. The friction hinge assembly of Claim 2, wherein said at least one band includes a segment having substan- tially the same configuration of said depression and which selectively overlies said depression.

4. The friction hinge assembly of claim 3, wherein said depression comprises a flat having a substantially planar contour.

5. The friction hinge assembly of Claim 4, wherein said at least one band segment comprises a planar member.

6. The friction hinge assembly of Claim 3, wherein said at least one band includes a first end leading into a tail and a second end.

7. The friction hinge assembly of Claim 6, wherein said second end of said at least one band comprises said segment.

8. The assembly of Claim 2, wherein said at least one band comprises a pair of bands.

9. The assembly of claim 1, wherein said shaft is connected to a first hinged element and said at least one band is connected to a second hinged element.

10. The friction hinge assembly of Claim 5, wherein said planar member of said at least one band is selectively seated along said flat of said shaft cylindrical member.

11. The friction hinge assembly of Claim 5, wherein said planar member is at one end of said at least one band and includes a leading edge.

12. The friction hinge assembly of Claim 11, wherein said edge of said planar member selectively contacts said flat of said cylindrical member.

13. The friction hinge assembly of Claim 2, wherein said depression comprises a substantially rounded cut-out.

14. The friction hinge assembly of Claim 1, wherein said camming enabling means comprises a protrusion formed along a portion of said cylindrical member.

15. The friction hinge assembly of Claim 14, wherein said at least one band includes an opening through which said protrusion selectively extends.