Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Element is tube with slot through wall to provide flexibility
Reexamination Certificate
2002-09-04
2004-01-27
Browne, Lynne H. (Department: 3679)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Element is tube with slot through wall to provide flexibility
C464S088000, C403S222000, C403S223000, C403S290000, C403S344000
Reexamination Certificate
active
06682432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the present invention relates:
generally to flexible couplings for rotary shafts transmitting torque via a flexible element;
more particularly to flexible couplings for rotary shafts transmitting torque via a flexible element facilitating angular misalignment; and
most specifically to the use of sleeve inserts in flexible coupling of rotary shafts with torque transmission via a flexible element that facilitates angular misalignment.
2. General Background
It is considered that the basic, fundamental, purpose of a flexible shaft coupling is the transmission of torque between drive and driven shafts possessing a small degree of angular misalignment between substantially aligned rotational axes. In this context it is next considered that flexible shaft couplings are used in a huge range of applications which can perhaps best be demarcated by one simple opposition between larger, dedicated, applications and smaller, variable, applications. The coupling of a drive shaft to a knuckle joint on a driven wheel of an automobile is considered exemplary of the first category. Other examples of similarly large, dedicated, applications include coupling of an airplane propellor or helicopter rotor to a power drive shaft. Opposed to this are flexible shaft couplings which are generally available with different bore sizes for coupling rotary shafts in precision power transmission, positioning control, and smaller power transmission devices including but not limited to: encoders, resolvers, DC tachometer generators, precision potentiometers, stepper & servo motors, XYZ tables, robotics, optics, laboratory, medical and business machines.
It is noted that in the second category flexible shaft couplings are typically used as ‘off the shelf’ components in the building of machines or for coupling the driven shaft of a device to the shaft of an electric motor for a temporary, unique, or otherwise various purpose. In either case the couplings are purchased in accordance with the diameter of the shafts concerned. The shafts, however, are not always of the same diameter. And if a flexible shaft coupling having the two different diameter shaft bores desired is available the expense may be considerable for what essentially must be a ‘special’ run for the flexible coupling manufacturer. Otherwise a flexible coupling having one bore which fits the smaller shaft is commonly used and the other bore is machined out to the larger diameter required.
It is further considered that ‘miniature’ shaft couplings intended for use in precision power transmission, positioning control, and smaller power transmission devices including but not limited to: encoders, resolvers, DC tachometer generators, precision potentiometers, stepper & servo motors, XYZ tables, robotics, optics, laboratory, medical and business machines are more economically molded in plastic than machined in metal, and in this case a ‘special run’ of flexible couplings having shaft bores which are not ‘stock’ is impractical as this requires a whole new set-up with a new mold, and a separate production run, as opposed to simply altering the bore concerned at the end of a routine, standard stock size, production run for just the number of units ordered in which case only the time necessary to make the single tool adjustment is incurred as an additional expense.
Another basic distinction, based upon the economics of manufacture concerned, is hence recognized between molded plastic flexible couplings and machined metal rotary shaft couplings. Molding is more economic in volume production and machining is more economically accommodative of variations, particularly with respect to bore diameter, as his is determined simply by the position of a tool during the routine manufacturing process while molding a different bore requires a whole new set-up with a new mold.
Discussion of the Prior Art
U.S. Pat. No. 949,189 issued to Hugo Lentz discloses a ‘universal coupling’ using a rectangular cross section ‘bush’ or sleeve which fits into the rectangular bore of the hub of a ‘rotary cylinder’ and into which a shaft having at least two exterior parallel opposed surfaces contacting interior opposed parallel surfaces of the ‘bush’.
The other two opposed parallel surfaces can also make contact, as shown in
FIG. 7
, but it is preferred that these surfaces have a ‘swell’ or outward smooth curved enlargement which contacts the bush interior walls and holds the shaft by tightening two set screws behind the ‘swells’.
French Patent 1306123 issued to M. Antelme discloses a coupling with a solid elastic body with two opposed blind hexagonal cavities into which a hex nut with a smooth bore is located with a radial pin through apertures in the coupling body and the nut.
A long bolt is apparently threaded through a tapped aperture through the middle of the pin for fixing the depth of the pin which, although shown to be smooth, clearly engages a tapped aperture in the nut and has a slot
10
on the end which would allow rotation with a flat blade screwdriver. The pin evidently passes through a transverse aperture through a shaft located in the bore of the nut or hexagonal insert and the long bolt could attach the shaft to the pin.
U.S. Pat. No. 3,395,552 issued to Hauser, Jr. discloses a flexible coupling having a stiff sleeve
8
fitted into an interiorly ‘serrated’ or splined bore of a flexible sleeve which is longer and is connected at either end to a shaft hub,
2
,
4
, by a pin
11
through opposed apertures
12
,
13
through the hub and ends of the flexible sleeve which reduces shock transmission and accommodates slight shaft misalignment while the stiff sleeve insert provides dampening at resonant frequencies.
Great Britain Patent 1 283 723 issued to Mayerjak discloses, as clearly seen in
FIG. 5
, a flexible coupling using a rubber sleeve between the exterior surface of a small diameter tubular member and the interior surface of a larger diameter tubular member which are mechanically connected by sets of arms: “Finally, in the embodiment described . . . the use of an elastomeric bushing
62
between the drive and driven shafts has the result of increasing the natural frequency of the overall coupling, and . . . provide a fail safe restraint in the event of failure of one or more of the flexing elements.” (Page 3, lines 35-49)
Soviet Union Patent 1106558 issued to the KRAMA Mechanical Engineering Research Institute discloses a ‘universal hinge’ or coupling for two rotary shafts, one having a split blade held by a ‘frictional insert’ in a bore of the other shaft which is held in an outer sleeve with a frictional insert. The outer sleeve contacts the exterior of the first shaft directly. The frictional inserts have curved exterior surfaces which apparently provide for two axes of rotation in accommodation of angular shaft misalignment.
U.S. Pat. No. 4,560,364 issued to Cohen discloses a ‘fail-safe improvement for a flexible coupling’ using a ‘plug’ which is threaded into one shaft and has a flange for retaining a tubular section of the second shaft in connection with the first if the primary, outward double wall flange, coupling fails. The plug is provided with a ‘head’ shown as a hex which facilitates tightening.
Statement of Need
Because smaller flexible shaft couplings typically used as ‘off the shelf’ components are often desired for applications in which two different diameter shafts must be coupled and because flexible shaft couplings having different shaft bores are often not readily available, particularly in molded plastic ‘miniature’ flexible shaft coupling suited for economic precision power transmission, positioning control, and smaller power transmission, it is considered desirable to be able to economically reduce the bore of a flexible shaft coupling, particularly the bore of a molded plastic ‘miniature’ flexible shaft coupling suited for economic precision power transmission, positioning control, and smaller power transmission which, because it is molded, cannot have a bore diameter economically
Browne Lynne H.
Gibson Peter
Thompson Kenneth
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