Shaft bushing and hub assembly

A bushing and hub assembly for mounting sheaves, sprockets, gears, couplings and similar machine elements on a shaft, wherein two types of tapered bushings are used, the bushings having bodies of the same taper used with a single hub which is compatible with both bushings. One of the bushings has a radially extending annular flange at the large end of the tapered body and the other bushing is flangeless. The screw holes and plain holes are provided in the flange and at the interface of the bushing and hub for securing the selected bushing in place in the hub for mounting the machine element on the shaft with screws for tightening the bushings securely in place on the shaft and in the hub bore. The two bushings and the sidewalls of the hub all have the same taper and are interchangeable with one another, to provide optimum performance and convenience of installation.

BACKGROUND OF THE INVENTION 
A well known structure for mounting sheaves, sprockets, couplings, gears 
and similar machine elements onto shafts consists of a tapered bushing 
having a longitudinal slit extending the length thereof and a cylindrical 
bore therethrough, for gripping the shaft internally and seating on a 
corresponding tapered surface in the bore of the hub of the machine 
element. There are generally two types of tapered bushings which are 
extensively used for securing the machine elements to the shaft, one 
consisting of a tapered body of a frustoconical shape secured in the hub 
bore, normally by two screws seated in holes intersecting the interface of 
the bushing and hub and having screw threads in the portion thereof in the 
hub and having a plain surface in the portion in the bushing. The screws 
abut against the end of the hole portion in the bushing and, when the 
screw is tightened, the end of the screw forces the bushing into the 
tapered bore of the hub, thereby causing the bushing to contract around 
and grip the shaft and to seat firmly onto the tapered surface of the 
bore. When the bushing has been secured in place in the machine element, 
the ends thereof are normally substantially flush with the respective ends 
of the hub, as are the heads of the securing screws. The bushings are 
removed from the bores of the hubs by one or more jackscrews seating in 
holes similar to the securing holes, except that the screw threaded and 
plain portions are reversed with respect to the bushing and hub, and the 
abutment for the jackscrews is in the hub. 
The other type of bushing is similar to the first one described above with 
respect to the tapered body, but instead of having the holes for the 
securing screws at the interface of the bushing and hub, the bushing has a 
radial annular flange disposed on the large end of the tapered body, 
usually containing three plain holes for receiving screws which extend 
through the flange into threaded holes in the end of the hub. The screws 
have heads thereon, and when the screws are tightened, they force the 
flange toward the end of the hub and the bushing body into the hub bore, 
thereby seating the tapered surface of the bushing on the tapered surface 
of the hub and contracting the bushing body onto the shaft. In the past, 
these two types of bushing were not interchangeable in the hubs of the 
various machine elements and hence, if both lines of bushing were to be 
made available to customers as on-the-shelf items, it was necessary to 
stock two lines of machine elements, such as sheaves, sprockets, couplings 
and gears, for the respective type of bushing. This not only increased the 
inventory of the various elements and parts for mounting them on the 
shafts, but also increased the fabricating, handling and storage costs. 
SUMMARY OF THE INVENTION 
It is one of the principal objects of the present invention to provide a 
combination bushing and hub structure which permits the interchangeability 
of the foregoing two types of bushings for any particular kind of machine 
element without requiring any structural modification in the parts thereof 
to fully adapt one or the other bushing to the particular hub, and to 
provide a combination bushing and hub structure in which at least one of 
the bushings can be secured in the hub bore by access to the securing 
means from either end of the hub. 
Another object of the invention is to provide a relatively simple system 
for utilizing both types of bushings in a single type of machine element 
hub, permitting the bushing types to be interchanged to adapt the machine 
elements to various applications and types of installation and to provide 
compatibility between the various types of hubs and machine elements for 
maximum cost saving in fabrication, handling and storage and for effective 
inventory reduction and control. 
The foregoing objects and other objects and advantages which will become 
apparent from the following description, are achieved by the combination 
of two types of tapered bushing with bodies of the same taper and a single 
hub which is compatible with both bushings, one of the bushings being 
flangeless and having two or more securing screws seated in holes at the 
interface of the bushing and hub, and the other of the bushings being 
provided with a radial, annular flange on the large end of the bushing 
body and preferably having three securing screws extending through the 
flange into threaded holes in the hub, or alternatively, extending through 
the hub into threaded holes in the flange. Jackscrews are normally 
utilized in both types of bushings for retracting the bushings from the 
bores in the hubs. In the flangeless type, one or more special holes are 
provided at the aforementioned interface for the jackscrew or screws, 
while in the flange type, one of the threaded sets of holes in the flange 
or hub is used for the jackscrews. The most suitable type of bushing can 
be selected for any particular application or installation, and the types 
of bushings can be interchanged in the field, if required or desirable, 
without changing the sheave, sprocket or other machine element in use.

DETAILED DESCRIPTION OF THE INVENTION 
Referring more specifically to the drawings and to FIG. 1 in particular, 
numeral 10 indicates a sheave, with shaft 12 and shaft bushings 14 and 16, 
the two bushings being interchangeable with one another in the bushing and 
hub assembly. While a V-belt sheave has been shown in the drawings, it is 
merely for the purpose of showing the present invention, which, in 
addition to a variety of different types of sheaves, is capable of being 
used with a variety of different shaft mounted machine elements including 
sprockets, gears and couplings. Throughout the description herein, 
reference will be made principally to a sheave or sheaves; however, this 
specific reference is for illustrative purposes only, and is not intended 
in any way to be a limitation to the types of shaft mounted machine 
elements to which the present invention is applicable. 
The sheave shown in the drawings has a hub 20 and a cylindrical portion 22 
joined integrally to the hub and having a plurality of V-belt grooves 24 
in the periphery thereof. The hub has a bore 26 with a tapered inner 
surface 28 for receiving either bushing 14 or 16 for mounting the sheave 
on shaft 12, shaft 12 having a key indicated by numeral 30 for matching 
keyways 32 and 32' in the two bushings and the shaft, respectively. The 
bushing 14 includes an annular body 40 having a tapered outer surface 
corresponding to the tapered surface 28 of the hub, and a slit 42 
extending axially and radially through the annular body 40, thus 
permitting the bushing to contract around the shaft in a manner to be more 
fully described later herein. The bushing 14 is inserted in the bore 26 
and screws 44 and 46, as shown in full in FIG. 8, are inserted into holes 
intersecting the interface of the hub and bushing, as shown in FIG. 9. The 
portion 48 of each hole in the bushing coincides with the threaded 
portions 50 in the inner surface of the hub. In the securing operation, 
the hub is started into the bore 26 and, after the sheave and bushing have 
been assembled around the shaft, the screws are threaded into the holes 
formed by the two half portions, and as the screws advance along the 
threads in the hub, the screws abut against the inner ends 51 of the hole 
portions in the bushing, forcing the bushing along the tapered surface of 
the hub, thereby contracting the bushing around the shaft. As the bushing 
contracts around the shaft, it grips the shaft and the tapered sidewall of 
the bushing seats firmly on the tapered surface of the bore 26, securing 
the hub to the bushing and the bushing to the shaft in a firm relationship 
to maintain the parts in assembled position on the shaft after the screws 
are fully tightened in their respective holes. One or more jackscrews are 
preferably provided for removing the bushing from the hub, the assembly 
shown in FIG. 1 having a threaded hole segment 52 and a plain hole segment 
54 in the bushing and hub, respectively. After the securing screws 44 and 
46 have been removed, a similar screw is inserted in the hole formed by 
half segments 52 and 54 and seats on the inner end of hole segment 54 in 
the hub, forcing the bushing axially relative to the hub to release it 
from the hub. The bushing just described is not provided with a radial 
flange and the ends thereof are normally substantially flush with the 
opposite ends of the hub when the bushing is secured fully in place. 
The hub is designed for the alternative and interchangeable bushing 16 so 
that either of the two bushings can be used in the assembly without any 
modifications or machining operations for adapting the hubs to a 
particular installation. Bushing 16 consists of an annular body 70 with a 
taper identical to the one on annular body 40 of bushing 14, and an 
annular, radially outwardly extending flange 72 formed or secured 
integrally to the large end of the tapered body 70. A slit 74 extends 
axially and radially through the body and flange, so that the bushing 
seats in the hub bore and can contract around the shaft in a manner 
similar to that described with reference to bushing 14. In using bushing 
16, the bushing and sheave are assembled on the shaft, and screws 76 are 
inserted through the three plain holes 78 extending through flange 72, and 
are threadedly received in matching threaded holes 80 in the end wall of 
the hub. As these three screws are tightened, the bushing is forced 
inwardly along the tapered surface of bore 26, which results in the 
bushing contracting around the shaft and the tapered surface of body 70 
seating firmly on the tapered surface of bore 26. While three holes are 
shown in the embodiment of the drawings, a greater number of holes may be 
used for larger shaft mounted machine elements if necessary or desirable. 
When the sheave is to be removed from the shaft, the screws 76 are removed 
from holes 78 and one or more of the screws are threaded through holes 82 
in the flange 72 seating on the adjacent end of hub 20. As the screws are 
tightened, the bushing and hub are moved relative to one another, thereby 
releasing the forces holding the hub on the bushing and the bushing on the 
shaft. The sheave and bushing can then readily be removed from the shaft 
and disassembled. 
The bushing 16 is capable of being assembled from either end of the hub, as 
illustrated in FIGS. 6 and 7, wherein the arrangement of FIG. 6 represents 
that previously described herein, and the arrangement of FIG. 7 represents 
the procedure of securing bushing 16 from the opposite end of the hub. In 
the latter arrangement, the screws 76 are inserted through three 
unthreaded holes 90 in the hub, and into matching threaded holes 82 in the 
flange of bushing 16. As the screws 76 of the arrangement shown in FIG. 7 
are tightened, the bushing is drawn into the tapered hole of the hub and 
secures the bushing to the shaft and the sheave to the bushing in the 
manner described hereinbefore. When the sheave is to be removed from the 
shaft, screws 76 are removed from holes 82 and 90 and inserted in threaded 
holes 80 and tightened to the point where the ends thereof seat against 
the flange on the opposite side of the hub. As the screws are further 
tightened, the bushing and hub are moved relative to one another, thereby 
releasing the hub from bore 26 and permitting the sheave and the bushing 
to be removed from the shaft. In order to permit the threaded holes 82 in 
the flange to be used to remove the bushing from the hub, as for example 
in the arrangement shown in FIG. 6, the holes 82 are not aligned with the 
unthreaded holes in the hub when the screws 76 are inserted through holes 
78 into holes 80 during the securing operation; thus, the screws 76, when 
functioning as jackscrews and inserted in holes 82 for removing the 
bushing, abut against the solid end of the hub, rather than in aligned or 
matching holes. This same relationship exists in the arrangement shown in 
FIG. 7. Thus, no special threaded holes are required for the jackscrews in 
order to obtain effective release of the bushing from the hub with the 
flange-type bushing 16. 
In the shaft bushing and hub assembly of the present invention, bushings 14 
or 16 can be selected for the most effective and convenient arrangement 
for mounting the sheave on the shaft, and the flanged bushing 16 can 
secure the sheave on the shaft from the end of the hub which is most 
convenient for making the installation, and which will give optimum 
performance of the sheave. If, in certain installations, the axial space 
available for the sheave is limited and the flange and heads of the screws 
of bushing 16 would interfere with the assembly, bushing 14 can 
effectively be used, since in the final installation of this bushing, it 
is substantially flush with the ends of the hub, thereby not requiring any 
additional space for the securing means. Since the two bushings 14 and 16 
are interchangeable with one another and require only a single hub design 
to fully utilize the advantages of the two bushings, the present dual 
bushing and hub arrangement permits the maximum versatility in adapting 
the sheave or other machine element to various applications and 
installations, while, at the same time, reducing the inventory needed to 
meet the requirements of the various applications. 
While only one embodiment and several modifications have been described 
herein, various changes and further modifications may be made without 
departing from the scope of the invention.