Clamping device

A clamping device for the fastening of a hub on a shaft, with a tapered flange ring having a cylindrical circumferential surface, with a conical circumferential surface radially opposing the surface and with a radial flange and with two taper parts capable of being tightened by means of axial clamping screws, with conical surfaces intended for cooperation with the tapered surface of the tapered flange ring. Control of the stress distribution along the shaft and security against overloads without slipping on the shaft are also obtained.

BACKGROUND 
1. Field of the Invention 
The invention relates to a clamping device, and more particularly to a 
clamping device for fastening an external structural part assembly to a 
shaft. 
2. Prior Art 
A clamping device of this type is known in the form of a so-called clamping 
set illustrated in German Specification No. 20 17 149. The relatively thin 
walled taper ring flange is located with its cylindrical inner 
circumferential surface on a shaft which constitutes the inner structural 
component. The conical part is in the form of a taper ring with its 
conical inner circumferential surface cooperating with the external 
circumferential surface of the taper ring flange and possessing a 
cylindrical outer circumferential surface arranged in a hub. 
It has been found in actual practice that the stress distribution along the 
shaft, i.e. the specific surface pressure whereby the taper ring flange is 
pressured against the shaft, is not as uniform as it should theoretically 
be, but that a strong increase in stress is experienced toward the thin 
walled end of the taper ring flange. This is especially true if in the 
tightened state the taper ring slightly protrudes in the axial direction 
past the thin walled end of the tapered flange. These high edge stresses 
are superimposed on the state of stress prevailing in the shaft as the 
result of the torque and possibly of bending stresses so that excessive 
relative stresses may occur in the area of the end of the tapered flange 
ring. These in turn may lead to plastic deformations and, in the case of 
rotating bending stresses, even to an alternating stress which in extreme 
cases may become the cause of cracking of the shaft. 
OBJECTS AND SUMMARY 
It is the object of the invention to further develop a clamping device in a 
manner such that the stress distribution along the axis may be affected in 
a certain degree, and in particular the excess stress at the end of the 
tapered flange ring may be avoided. 
The basic concept consists of eliminating the excessive increase in stress 
taking place in the case of a conical part extending essentially over the 
axial length of a tapered flange at its end, upon tightening to a 
predetermined clamping level. This is accomplished by dividing the conical 
part into several separately actuable conical parts, wherein the conical 
parts near the flange may be tightened to the extent required to assure 
the transfer of a predetermined torque, while the conical part arranged at 
the height of the free end of the tapered flange ring is tightened 
independently of the former only to a degree necessary for the attainment 
of permissible surface pressures. In this manner, the stressing of the 
conical part or parts adjacent to each other in the flange may be effected 
to a level necessary for the transfer of the torque desired, without 
having unacceptably high edge stresses. 
In conical clamping devices of the above mentioned type fundamentally two 
configurations are known. The outer structural component assembly may have 
a conical surface itself which cooperates with the external conical 
surface of the tapered flange ring. One embodiment of the invention 
includes the outer conical surface of the tapered flange ring where two 
structural parts are located possessing internal conical surfaces seated 
directly on the conical surface of the tapered flange ring. The "conical 
part" and the "outer structural part" are thus identical. 
Since in actual practice the parts of the clamping device itself are 
normally made by a manufacturer other than the manufacturer of the 
structural parts to be clamped and the latter usually purchases the parts 
of the clamping device in the form of a complete unit, and further since 
it is possible to correlate the conical surfaces in relation to the angle 
of inclination and surface quality with the accuracy required with great 
effort only, clamping devices of this type are frequently designed as 
so-called clamping sets. These include their own conical rings with a 
cylindrical circumferential surface cooperating with the tapered flange 
ring. The outer structural part in this case does not act directly in 
cooperation with the conical surface of the tapered flange ring, but 
merely has a cylindrical bore into which the "clamping set" is inserted. 
Cylindrical bore holes do not pose problems with regard to alignment. 
The term "structural part arrangement" comprises both the case wherein a 
single piece structural element with a cylindrical recess is involved, 
with two taper rings located on a tapered flange ring cooperating with it, 
and the case where there are, for example, two separate structural 
elements arranged in succession in the axial direction, with at least one 
of them located on a taper ring. 
This form of embodiment of the clamping device according to the invention 
provides an important additional advantage that may be of great importance 
in many cases. If, for example, in the embodiment of DE-OS No. 20 17 149, 
FIG. 1, with identical slide pairings being assumed on the shaft and in 
the hub bore (overwhelmingly steel), the torque transmitted increases, 
slipping will always occur first on the shaft as its radius is smaller. 
Correspondingly, for a given torque the circumferential forces that must 
be held by friction are larger. Slipping on the shaft is, however, 
extremely undesirable in many cases, as the shaft will be damaged by 
scoring and the removal of the clamping device made more difficult. 
The aforementioned embodiment offers the possibility of providing safety 
against an overload, without slipping occurring on the shaft. Rather, the 
outer structural element seated on the taper ring slips on its cylindrical 
surface. This is obtained by the fact that the tapered flange ring is held 
on the shaft, not exclusively by the radial forces acting on the 
structural element involved, but also by the radial forces acting between 
the tapered flange ring and the adjacent structural part. The tapered 
flange ring is thus held to some extent additionally on the shaft by 
artificial means, so that it does not slip under the effect of a torque 
applied to a structural element, and slipping occurs first on the 
cylindrical surface of the taper ring associated with the structural 
element involved, i.e. outside the shaft. 
Layouts with structural elements arranged adjacent to each other on a shaft 
are rather common, for example in adjacently placed toothed gears, chain 
gears and crank gears with the drive wheel adjacent to the crank. 
The clamping device is tightened by means of axial straining screws 
distributed over the circumference and passing through the flange of the 
tapered flange ring. Accordingly, for the tightening of two conical parts 
or taper rings seated on the same taper flange ring, two sets of such 
straining screws must be present. As the number of straining screws that 
may be placed on the circumference of the flange is limited, the number of 
straining screws acting on each individual conical part or taper ring is 
also restricted to approximately one-half of the maximum number. The 
maximum axial tensile force and correspondingly the radial clamping force 
and the transferable torque are also limited. 
Another embodiment of the invention includes a large number of straining 
screws for each individual conical part or taper screws. 
The conical part adjacent to the flange is initially tightened by means of 
straining screws with larger diameters, distributed over the circumference 
without appreciable intervals (with the possible exception of forcing 
threads) to the tightness desired. These straining screws are then removed 
while the clamping remains because of the self-locking of the cone angle. 
Subsequently, the auxiliary ring is placed in front of the flange, and the 
straining screws with the lesser diameter are screwed through the passage 
bore holes of the flange and the threaded bores of the conical part 
adjacent to the flange into the threaded bores of the next conical part 
and tightened. In this manner, every conical part may be tightened by 
means of a full set of straining screws completely filling out the 
circumference. 
In order to equalize the lesser diameter of the second set of straining 
screws, the part removed from the flange of the tapered flange ring and 
the conical part cooperating with it may have a reduced angle of 
inclination of the cone. The radial force obtainable with a given axial 
force is then correspondingly higher. 
Yet another embodiment is of special importance in cases in which the 
limited mechanical strength of a structural part renders it difficult to 
achieve adequately high clamping forces. This is the case, for example, 
when the hubs are made of gray cast iron or aluminum. Here, by virtue of 
the invention of the structural element involved may be loaded to a still 
permissible radial stress and an appreciable additional frictional lock 
generated, which also benefits the first structural part.

DETAILED DESCRIPTION 
In the clamping device illustrated in FIG. 1 and designated in its entirety 
by 100, a tapered flange ring 1 is present; it rests with its cylindrical 
internal circumferential surface 2 on a shaft (not shown). On the opposite 
side, the tapered flange ring 1 has an outer conical surface 3, the apex 
of which is to the right in FIG. 1, so that the thick walled end of the 
tapered flange ring 1 is located to the left, on the side of a radial 
flange 4 protruding on the side of the conical surface 3, i.e. to the 
outside. The radial flange 4 has a plurality of passage bores 5 
distributed over the circumference, through which a plurality of clamping 
screws 6, 6' and optionally unclamping screws (not shown) pass. The 
tapered flange ring 1 is provided at one point with a longitudinal slit 7, 
so that it is readily deformed in the radial direction, and the clamping 
force of the screws 6, 6' is not lost merely to deform the tapered flange 
ring 1. 
On the tapered flange ring 1, adjacent to the flange 4, a first taper ring 
8 with an internal conical surface 9 cooperates with the conical surface 
3. It further has an outer cylindrical circumferential surface 10 arranged 
over it. The first taper ring 8 contains a plurality of passage bores 11 
for the clamping screws 6 and a plurality of threaded bores 11' for the 
clamping screws 6'. The clamping screws 6' draw the taper ring 8 to the 
left in accordance with FIG. 1, whereby the conical surfaces 9, 3 slide on 
each other, and the taper ring 8 is expanded radially. In order to 
facilitate this deformation, the taper ring 8 has a longitudinal slit (not 
shown). 
Positioned adjacent to the taper ring 8 in the axial direction, on the 
tapered flange ring 1, is a second slit taper ring 12 with an inner 
conical surface 13 and a cylindrical outer circumferential surface 14. The 
taper ring 12 comprises a plurality of threaded bores 15 for the clamping 
screws 6. The latter screws pass through the taper ring 8 and engage the 
taper ring 12 in order to draw it to the left in FIG. 1 with a force that 
may be adjusted independently of the clamping screws 6'. 
The two cylindrical outer circumferential surfaces 10, 14 of the taper 
rings 8, 12 rest against a cylindrical inner circumferential surface 21 
which has the same diameter as the recess of an outer structural element, 
which in the example shown on top in FIG. 1 is a single piece structural 
part. Upon the tightening of the clamping screws 6, 6', the shaft (not 
shown) is fixedly secured in rotation in the recess 21 by a frictional 
lock. 
The taper ring 8 near the flange may be tightened by means of the clamping 
screws 6' with any force that may be desired. The tightening force of the 
taper ring 12 may be regulated independently of the foregoing by means of 
the clamping screws 6, so that the unacceptable peak stress otherwise 
readily appearing at the end to the right in FIG. 1 of the tapered flange 
ring 1 is avoided. 
As illustrated in the lower half of FIG. 1 the diameters of the cylindrical 
surfaces 10, 14 may also be different, as shown by the broken line 14', so 
that the bore 21 is a stepped bore hole. In particular, however, the outer 
structural element layout represented in the upper half of FIG. 1 by the 
single piece part 20, may also consist of a pair of structural elements 
20',20", which abut against each other in a radial plane 22 or else are 
spaced apart axially, as indicated by the broken line. Each element 
20',20" is associated with a taper ring 8 and 12. But the two elements 
20', 20" are seated on a common tapered flange ring 1. 
This configuration makes it possible to provide an overload safety feature, 
whereby in the case of an overload, slipping takes place, but not on the 
shaft. If a torque acts on one of the structural elements 20', 20", which 
in view of a given state of stress can no longer be transmitted by means 
of a friction lock involving for example the element 20", the latter will 
slip on the cylindrical circumferential surface 14 and not on the shaft. 
This is because the tapered flange ring 1 is clamped to the shaft in 
addition to the radial forces transmitted by the taper ring 12 and also by 
the radial forces transmitted by the taper ring 12, thereby corrspondingly 
raising its slipping threshold. 
To the extent that in the forms of embodiment hereafter identical parts are 
present, identical reference symbols are applied. 
The principal difference of the clamping device 200 of FIG. 2 relative to 
the clamping device 100 of FIG. 1 consists of the fact that a conical 
inner circumferential surface 31 is applied directly to a structural part 
30 near the flange, i.e. no separate taper ring is provided which would be 
arranged in a cylindrical recess of the part 30. This results in the fact 
that the structural part layout is no longer separable from the clamping 
parts and that the clamping device 200 does not comprise a separate 
clamping set 16 forming in itself a closed unit, as in FIG. 1. Otherwise, 
the clamping device 200 also has two structural elements 20", 30, arranged 
adjacent to each other in the axial direction, but spaced apart, wherein 
an overload safety feature is again provided for the part 20" in a similar 
manner by slipping on the cylindrical circumferential surface 14 of the 
taper ring 12, as in FIG. 1. 
A further difference of the clamping device 200 resides in the fact that 
the element 30 rests against the flange 4, as is the case of location 17 
in FIG. 1 with respect to element 20'. This in turn results in the fact 
that upon the tightening of the clamping screws 6, 6' the structural 
elements 30 and 20" are displaced to the left a small distance with 
respect to the shaft (not shown). In many cases this is immaterial. The 
advantage is that sliding takes place along the conical surface 3 only, 
and the friction must be overcome at this location only. In the form of 
the embodiment according to FIG. 1, upon the tightening of the screws 6, 
6' sliding takes place both on the conical surface 3 and on the inner 
circumferential surface 21 of the outer structural part 20. Even though, 
due to its abutting at 17, the outer structural part 20 remains exactly at 
its location, the greater part of the clamping force is lost to friction. 
In the clamping device 300 of FIG. 3 the element 20' is again seated on the 
taper ring 8. The clamping screws 6 directly engage the element 32 so that 
a rotation of the latter is thereby prevented. However, the flange cone 
bushing 1 also clamps the shaft (not shown) so that slipping may take 
place only on the cylindrical surface 10. The inner conical surface of the 
structural element 32 is formed by a relatively thin walled, tapered and 
slit insert 33, which is inserted in a cylindrical bore 34 of the element 
32 and secured by a collar 35 against slipping under the effect of the 
clamping screws 6. 
While the taper ring 1 in FIGS. 1 to 3 is seated with its cylindrical inner 
circumferential surface 2 on the shaft (not shown), in FIG. 4 a taper ring 
41 has a cylindrical outer circumferential surface 42 resting against the 
inner circumference 21 of the outer structural element 20. A conical 
surface 39 of the tapered flange ring is the internal tapered surface and 
is cooperating with the outer taper surfaces 43, 44 of taper rings 45, 46, 
which are seated with their cylindrical inner circumferential surface 47, 
49 on the shaft (not shown). The radial flange 40 is pointed inward. 
The clamping device 400 is applicable only to single piece outer structural 
parts 20 and is only able to reduce the peak stress at the edge to the 
right in FIG. 4 of the tapered flange ring 41 in the manner described for 
FIG. 1, but not as a safety against overloading. As however the problem of 
the edge stress peak on the side of the hub, i.e. when the relatively thin 
walled tapered flange ring is not seated directly on the shaft, is not 
that great, the clamping device 400 should not be considered an important 
form of embodiment, even though it embodies the concept of the invention. 
To release the clamping devices described above, longer forcing or 
unclamping screws are screwed into the short clamping screws 6', pressing 
against the locations without threads of the right hand taper rings. In 
this manner, the right hand taper ring may be forced off. To pressure the 
left hand taper rings off, forcing threads (not shown) are provided in the 
flange 4, 40, into which the unclamping screws may be inserted. They press 
against locations of the left hand taper rings without threads, thereby 
forcing or unclamping them off the tapered flange ring. 
The clamping device 500 of FIG. 5 essentially corresponds to the clamping 
device 100 of FIG. 1. The principal difference is that straining screws of 
two different diameters are used. The taper ring 8' comprises a plurality 
of threaded bores 11" having diameters such that the threaded bolts with 
the smaller diameter used may be inserted through them, whereby they serve 
as passage bores. The passage bore 5' in the flange 4 of the tapered 
flange ring 1 is again dimensioned for the larger diameter. The threaded 
bores 15 in the taper ring 12 correspond to the lesser screw diameter. For 
example, the larger screw diameter may amount to 14 mm, the smaller to 10 
mm. 
In the course of tightening the clamping device 500, which again represents 
a clamping set 16 forming a single unit, initially an auxiliary ring 50 
resting against the outer frontal side of the flange 4 is eliminated. The 
taper ring 8' is drawn to the left onto the tapered flange ring 1 to the 
degree of clamping desired by means of the straining screws with the 
larger diameter, according to FIG. 5. If the straining screws with the 
larger diameter now remain loose, the tape ring 8' remains under stress, 
as the angle of inclination of the conical surface 3 is within the 
self-locking range. The auxiliary ring 50 is now placed in front of the 
flange 4, and the longer clamping screws 6 are screwed into the threaded 
bores 15 of the taper ring to the right in FIG. 5 through the passage 
bores 52 and 5' and the threaded bore 11" of the taper ring 8', whereby 
the taper ring 2 is tightened. The advantage of this layout consists of 
the fact that the pitch circle for the clamping screws may be fully 
utilized for both of the two taper rings 8' and 12, while in the forms of 
embodiment of FIGS. 1 to 4 the clamping screws 6' must be set between the 
clamping screws 6, whereby only one-half of the clamping screws remains 
available. Obviously, in both cases room must be provided for a certain 
number of unclamping screws 51. 
The clamping device 600 of FIG. 6 essentially corresponds to the clamping 
device 500, with the single difference that the conical surface 3 of the 
tapered flange ring 1 is divided into sections 3' and 3" in the axial 
direction, with the angle of inclination of both being located in the 
self-locking range, but with the angle of inclination of the section 3", 
located under the right hand taper ring 12 removed from the flange, being 
slightly smaller than that of the section 3'. Naturally, the angles of 
inclination of the conical surfaces of the taper rings 8' and 12 are 
suitably adapted. Due to the smaller angle of inclination of the section 
3", higher radial pressures may be obtained in spite of the smaller screw 
diameters used for tightening. 
Concerning the configuration of the external structural part layout not 
shown in FIGS. 5 and 6 the description given for FIG. 1 is valid. If a 
single piece structural element is involved which is engaged by two taper 
rings, the aspect of the effect on the stress distribution and the 
reduction of edge stresses are decisive. In the case of two structural 
elements arranged adjacent to each other, security against overloading is 
important. If only one structural part is present on one of the taper 
rings and the other, which then is unslit, is located outside the 
structural part, only overload security is involved. The other taper ring 
merely provides additional clamping of the tapered flange ring on the 
shaft. 
FIG. 7 shows a clamping device 700 serving to secure a structural part 20", 
for example a rope pulley, a toothed wheel, or the like, on the shaft W 
for the transmission of high torque. The structural part 20" is made of a 
material that is not particularly resistant to the radial stresses 
generated, for example by gray cast iron or aluminum. The clamping device 
700 essentially corresponds to the configuration shown at the bottom of 
FIG. 1, with the difference that both elements 20', 20" are joined in 
rotation to each other by means of axial bolts 54. The structural element 
20" is clamped onto the taper ring 1 by means of the slit taper ring 12 
and the clamping screws 6, which is still permissible in view of the 
material of the element 20". The axially adjacent part 20' consists of an 
unslit steel ring, capable of applying considerable radial forces. By 
tightening the taper ring 8 by means of the screws 6', significant 
clamping may thus be obtained. The torque that the rings 8, 20' are 
capable of holding also benefits the element 20", as the latter is joined 
with the element 20' in rotation by means of the bolts 54. 
While several embodiments of the invention have been described, it will be 
understood that it is capable of still further modifications and this 
application is intended to cover any variations, uses, or adaptations of 
the invention, following in general the principles of the invention and 
including such departures from the present disclosure as to come within 
knowledge or customary practice in the art to which the invention 
pertains, and as may be applied to the essential features hereinbefore set 
forth and falling within the scope of the invention or the limits of the 
appended claims.