Polygon connection of a hub with a shaft

A polygonal connection for joining a hub with a shaft includes a bore in the hub and a joining portion on the shaft. In one embodiment both the bore and joining portion have mating, non-circular polygonal cross sections. In that embodiment, radially expandable fasteners are located in the vicinities of corners of the polygonal cross section of the joining portion of the shaft. In another embodiment, the bore in the hub and the joining portion of the shaft have circular cross sections, and at least one radially expandable fastener is located on the circumference of the joining portion of the shaft. In both embodiments, each fastener runs parallel to the axis of the shaft, and the longitudinal axis of each fastener is disposed within the perimeter or circumference of the joining portion of the shaft.

TECHNICAL FIELD OF THE DISCLOSURE 
The invention concerns hub and shaft connections in which the shaft as well 
as the mating bore of the hub are both of circular cross section and are 
connected by means of at least one fastener arranged parallel to the axis 
of the shaft. 
DESCRIPTION OF THE PRIOR ART 
A known connection consists of an arrangement wherein both the shaft and 
also the bore of the hub are circular in their cross sections, but 
expandable bolts are inserted in the circumference, parallel to the axis 
of the shaft. The bolts have their centers located on the circumference of 
the shaft. They engage the hub with one of their halves and engage the 
shaft with the other of their halves, thus arresting them with respect to 
each other. Their deflection behavior is similar to that described in the 
preceding paragraph. 
SUMMARY 
It is the object of the invention to reduce the danger of deflection in the 
above-mentioned connections. 
In the present invention, there are fasteners which extend in directions 
parallel to the axis of the shaft. Each fastener includes means for 
effecting radial expansion thereof, and the fasteners have longitudinal 
axes located within the perimeter of the joining portion of the shaft. 
The action of this arrangement is based on frictional contact. Such 
frictional contact prevents the minimal displacements of the shaft with 
respect to the hub, which minimal deflections may lead up to substantial 
displacements and substantial stresses. It is essential for this purpose 
to locate the axis of the expandable bolt within the perimeter of the 
shaft or shaft joining portion, so that, during the expansion, the 
peripheral areas of the shaft are urged outwardly, thus engaging the bore 
of the hub. 
For the aspect of the invention, whereby the hub bore and the shaft or 
shaft joining portion have circular cross sections and are connected by 
means of expandable fasteners in the form of generally cylindrical bolts 
arranged on the circumference of the shaft, the solution according to the 
invention will now be briefly described. Of course, the joining portion of 
the shaft fits within the bore of the hub, and the circular cross sections 
of the bore and shaft joining portion are taken in planes normal to the 
axes of the hub and shaft. The joining portion of the shaft has a 
circumference defining the circular cross section thereof. The fastening 
is accomplished by at least one fastener or bolt disposed in parallel 
relationship to the axis of the shaft and on the circumference of the 
shaft joining portion. The fastener extends into both the hub and the 
joining portion of the shaft, the fastener having a longitudinal axis 
located radially within the circumference of the joining portion of the 
shaft. The fastener includes a means for effecting radial expansion 
thereof. 
Here, the fact that the peripheral areas of the shaft adjacent to the bolt 
are radially expanded, thus superposing frictional contact on the form fit 
of the connection, contributes to the effectiveness of the arrangement of 
the present invention. 
An important aspect of the invention resides in the fact that shaft-hub 
connections not only may be designed originally in the manner of the 
invention, but also may have the bolts of the invention added later to 
connections that are endangered by deflection, so that they may be 
reinforced. 
The radial expansion of the fasteners is effected by a plurality of 
interfitting cooperating conical parts in each fastener. Each fastener 
includes an outer sleeve with a pair of conical recesses disposed therein 
in opposed relationship to each other. Each fastener also includes a pair 
of conical elements, one of which is disposed in one of the conical 
recesses for cooperation therewith, the other of which is disposed in the 
other of the conical recesses for cooperation therewith such that the 
conical elements are disposed in opposed relationship to each other. Each 
fastener also includes a lock screw extending between the pair of conical 
elements for imparting an axial tightening force thereto, whereby the 
axial forces on the conical elements are translated into radial forces on 
the outer sleeve to effect radial expansion of the fastener. 
The aforementioned interfitting conical parts have a self-locking angle 
above which the parts are free to move axially after release from an axial 
force thereon. The interfitting conical parts also have half angles 
defined by the angles between the conical surface and the axis of each 
such part. The conical recesses of the outer sleeve also have half cone 
angles, and these half cone angles are in excess of the self-locking 
angles. Each conical element includes a conical ring with an internal 
conical passage having a half cone angle which is less than the 
self-locking angle and a conical plug arranged in the internal conical 
passage and having a half cone angle corresponding to that of the internal 
conical passage. 
The outer sleeve of each fastener and each conical ring thereof are 
longitudinally slit. The conical plug, however is free of any longitudinal 
slit. 
The outer sleeve includes an inner collar between the conical recesses of 
the sleeve. The inner collar is of such size and configuration relative to 
the conical recesses that the conical rings initially abut against the 
inner collar when axial tightening force is applied by the lock screw. 
The lock screw includes a threaded end and a driving end opposite to the 
threaded end, one of the conical plugs having an opening through which the 
lock screw extends. The other of the conical plugs has a threaded hole 
which is engaged by the threaded end of the lock screw. 
In one particular type of connection, each fastener includes a pair of 
radially expansible members which are axially aligned with each other and 
disposed in opposed relationship relative to one another. One of the 
radially expansible members cooperates with a first bolt which extends 
into the joining portion of the shaft from one end thereof. The other of 
the radially expansible members cooperates with a second bolt which 
extends into the joining portion of the shaft from the other end. Thus, 
the first and second bolts are in opposed relationship.

DETAILED DESCRIPTION 
In FIG. 1 a hub 1 is represented, which is located on a gear 2 or a similar 
structural part. Hub 1 has a bore 3 with a generally triangular cross 
section composed of circular arcs. By means of this bore 3, the hub 1 
rests on a suitably designed shaft 4, shaft journal or joining portion 
which fits into the bore 3 and which has a shape corresponding to that of 
the bore 3. 
In the vicinity of the three corners of the shaft 4, defined by the 
generally triangular cross section of the shaft, but still entirely within 
its perimeter, expandable fasteners 20 in the form of bolts are provided 
in corresponding bores parallel to the axis of the shaft 4. During their 
expansion, the expandable fasteners 20 urge the areas of the periphery of 
the shaft 4 located adjacently to the fasteners 20 in the radially outward 
direction, as indicated by the arrows 5. The external perimeter of the 
shaft 4 is thereby pressured against the internal circumference of the hub 
bore 3 under a compressive stress. 
The form of embodiment of FIG. 2 differs from that of FIG. 1 only in that 
the fasteners 20 project to some extent past the perimeter of the shaft. 
However, their axes are still within this perimeter, so that in the 
process of the expansion of the fasteners 20 the peripheral areas of the 
shaft 4 adjacent to the fasteners 20 are dislocated outwardly in a manner 
as shown with the arrows 5. 
In the exemplary embodiment of FIG. 3, the shaft or shaft portion 4' and 
the hub bore 3' are circular in cross section. The polygonal connection is 
effected by means of three fasteners or bolts 20 arranged parallel to the 
axis of the shaft 4', which fasteners are distributed in regular intervals 
over the circumference of the shaft 4' and which extend both into shaft 4' 
and the hub 1'. However, the axes of the fasteners are within the 
circumference of the shaft 4' so that during the expansion of the 
fasteners 20, the adjacent areas of the circumference of the shaft 4' are 
expanded in the direction of the arrows 5, in a manner similar to that in 
the embodiments of FIGS. 1 and 2. 
In FIG. 4, the embodiments of FIGS. 1 and 2 are shown in longitudinal 
sections. The hub 1 here belongs, for example, to a drum bottom. The shaft 
4 is, in its left hand area in FIG. 4, turned or ground into its 
non-circular form shown in FIGS. 1 and 2. In the upper half, the fastener 
20 is arranged in accordance with FIG. 2, i.e., it projects somewhat past 
the perimeter of the shaft 4. Its axis lies, however, clearly within the 
perimeter of the shaft 4. In the lower half, the fastener 20 is arranged 
as per FIG. 1 entirely within the shaft 4 in the region of one of the 
corners. 
The embodiment of FIG. 5 is based on the principle of FIG. 3. The hub 1' is 
represented by a gear and the shaft 4' by a shaft journal or shaft joining 
portion somewhat enlarged in its diameter. The shaft journal 4' 
corresponds in its length to the width of the hub 1. In each case, two 
bolts are arranged, which penetrate the shaft 4 from different sides. The 
cross section of the hub bore 3' and also that of the external outermost 
circumference of the shaft 4' are circular and essentially of the same 
diameter. The axes 6 of the fasteners 20 are within the external outermost 
circumference of the shaft 4'. 
In FIG. 6 there is shown in detail an exemplary fastener 20 in the form of 
a generally cylindrical bolt, suitable for the invention. It comprises a 
sleeve 10 longitudinally slit on one side. Sleeve 10 is provided with 
conical recesses 11 opposing each other from the two ends. Recesses 11 
have half cone angles of 17.degree., i.e., they are tapered clearly in 
excess of the self-locking angle. Each conical recess 11 contains a 
conical ring 12, also with a longitudinal slit and an internal conical 
passage 13 with a half cone angle of 5.degree., i.e., clearly less than 
the self-locking angle. In each conical passage 13 a conical plug 14 is 
arranged, which is not slit. The conical plug 14 on the left in FIG. 6 has 
an opening for the lock screw 15 to extend through. The conical plug 14 to 
the right in FIG. 6 includes a threaded hole which is entered by the lock 
screw 15. Dimensions are such that, during the tightening of the lock 
screw, the conical rings 12 initially abut against the inner collar 16 of 
the conical sleeve 10, and only the conical plugs 14 apply pressure 
against the surfaces of conical passages 13 with their angles of 
inclination that are less than the self-locking angle. This results in 
large radial expansion forces. The release of the lock screw 15 leads to 
an automatic release along the surfaces of conical recesses 11 of the 
entire arrangement in view of the surfaces of recess 11 being at an angle 
which is less than the self-locking angle. 
It is obvious that in place of the triangular arrangement shown in the 
examples of embodiment, other numbers of fasteners 20 distributed over the 
perimeter or circumference of the hub may be applied and that the 
fasteners 20 themselves may be of a design different from the one shown in 
FIG. 6.