Feeding device having alternatively connectable slip-on gear units

In order to simplify the construction and to accelerate the change-over of two drive units in the case of a feeding device having a drive shaft and two gear units each drivable by a motor, which gear units are able to be connected alternately to the drive shaft such that each may alternately rotate with the drive shaft independently of the other, it is suggested that both gear units are designed as slip-on gear units and have a driven hollow shaft, that the two ends of the drive shaft each have the hollow shaft of one of the two slip-on gear units mounted around them in a manner permitting relative rotation, that the gear units are secured against rotation about the axis of rotation defined by the drive shaft and that rotary couples are provided, such that one of the hollow shafts at a time is connected to the drive shaft such that the connected hollow shaft secured against rotation relative to the drive shaft.

The invention relates to a feeding device comprising a drive shaft and two 
gear units each drivable by a motor, which gear units are able to be 
connected alternately to the drive shaft such that each may alternately 
rotate with the drive shaft independently of the other. 
In the case of feeding systems, for example conveyor belts, block chain 
conveyors or lifting stations, drive is in general effected via a drive 
shaft, to which driving force is fed from an electric motor via a gear 
unit. In order to reduce interruptions during operation to a minimum, it 
is known to associate with such a drive shaft two gear units, each driven 
by its own motor, which gear units may be connected alternately to the 
drive shaft such that each may alternately rotate with the drive shaft 
independently of the other. If one of the drive units consisting of motor 
and gear unit fails, it is possible, and involves relatively little work, 
to connect the other drive unit to the drive shaft. 
In the case of a known construction, for example, two drive units mounted 
next to the operating device are separately connectable to a sprocket 
wheel on the drive shaft via a chain connecting gear. When the main drive 
unit fails, the chain can be taken off and laid over the other drive unit 
via its corresponding sprocket wheel. The disadvantage of this 
construction is that the connecting gear chain has to be greased and 
therefore requires a great deal of maintenance. In addition, the 
connecting gear chain must be covered by a protective casing, which has to 
be removed before the chain is transferred to the other drive unit. The 
use of a chain connecting gear also requires the use of a chain tension 
device so that the construction work involved is quite considerable. 
In the case of another known construction, the two drive units are mounted 
on the same base plate which is displaceably mounted substantially at 
right angles to the axis of the drive shaft. A spur gear is located on the 
drive shaft; both drive units have an output shaft with a spur pinion. By 
displacing the base plate, the spur gear on the drive shaft can mesh 
alternately with the spur pinion of either of the two drive units. In the 
case of this construction as well, greasing of the gear drive and covering 
of the same by means of a protective casing are absolutely necessary. A 
relatively large frame is required to accommodate the two drive units and 
this must also be displaceably mounted. In order to reduce the wear on the 
spur gears it is necessary to work with very narrow tolerances since this 
is the only way to guarantee that the spur gears meshing with each other 
operate free of play. 
SUMMARY OF THE INVENTION 
The object of the invention is to improve a feeding device of this type 
such that the change-over from one drive unit to the other can be carried 
out as quickly and easily as possible and that the construction of the 
driving gear is kept altogether simple. This object is solved for a 
feeding device of the type described at the beginning of this 
specification in that both gear units are designed as slip-on gear units 
and have a driven hollow shaft, the two ends of the drive shaft each have 
the hollow shaft of one of the two slip-on gear units mounted around them 
in a manner permitting relative rotation, the gear units are secured 
against rotation about the axis of rotation defined by the drive shaft, 
and rotary couples are provided, such that only one of the hollow shafts 
at a time is connected to the drive shaft such that the connected hollow 
shafts is secured against relative rotation with respect to the drive 
shaft. 
With this construction according to the invention the drive shaft itself 
has a drive unit at each end, which comprises a slip-on gear unit with a 
driven hollow shaft. This hollow shaft is mounted for free rotation on the 
shaft end. Due to a rotationally fixed connection one hollow shaft of the 
two drive units can be connected at a time to the drive shaft so that it 
is secured against relative rotation with respect to the drive shaft. In 
order to change over from one drive unit to the other it is merely 
necessary to release the rotary couple of one hollow shaft from the drive 
shaft and engage the rotarly couple of other hollow shaft instead to the 
drive shaft. 
It is advantageous to have each hollow shaft bearing a sprocket wheel, 
adjacent to each of which is a sprocket wheel having the same diameter and 
the same number of cogs and being mounted on the drive shaft such that it 
is secured against rotation relative to the drive shaft and to have a 
roller chain placed over the adjacent sprocket wheels to connect one 
hollow shaft and the drive shaft such that they are secured against 
relative rotation. This is preferably designed as a duplex chain. 
It is advantageous to have each hollow shaft mounted on the end of the 
drive shaft by means of at least two ball bearings. 
In a preferred embodiment the securing of each gear unit against relative 
rotation allows a limited rotation of the gear unit contrary to the action 
of an elastic pressure spring and a limit switch is provided for the motor 
associated with each gear unit, which is activated by the gear unit or a 
part rigidly connected to it when a specific rotation of the gear unit 
contrary to the action of the elastic pressure spring is exceeded due to a 
specific torque transmitted from the gear unit to the drive shaft being 
exceeded. Preferably, the gear unit is provided with an arm projecting at 
right angles to the axis of rotation of the drive shaft, a pressure spring 
being supported on this arm, this pressure spring extending substantially 
at right angles to the arm, its other end abutting on the frame of the 
machine; the limit switch is supported on the frame of the machine such 
that it is activated by the arm when a specific compression of the 
pressure spring is exceeded. 
A particularly simple possibility of limit switching in the case of 
overloading is achieved due to the positioning, according to the 
invention, of the gear unit on the drive shaft itself. 
It is advantageous for the end areas of the drive shaft, onto which the 
hollow shafts of the gear units are slipped, to have a smaller diameter 
than the remaining shaft. 
The following description of preferred embodiments of the invention in 
conjunction with the drawings is intended to give a more detailed 
explanation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The driving gear described in the embodiment is intended for a feeding 
device, for example a conveyor belt, block chain conveyor, lifting device 
or any other feeding device, which is driven by a drive shaft. This drive 
can, for example, be effected via a drive chain, which is guided on a 
sprocket wheel connected to the drive shaft so as to be secured against 
rotation relative to the drive shaft. 
In the embodiment shown in FIGS. 1 and 2 the actual feeding device is not 
illustrated. Shown are the two ends of a drive shaft 1, which is mounted 
on a frame 2 by two ball bearings 3, 4 so as to be secured against 
rotation relative to the frame. The drive shaft 1 extends on both sides 
beyond the ball bearings 3 and 4 which are secured to the machine and the 
drive shaft end portions have a smaller diameter than the rest of the 
shaft. 
A drive unit 5, 6 is slipped on to each end of the drive shaft, each drive 
unit comprising a motor 7 and a gear unit 8. 
The gear unit 8 is disposed within a housing 9, in which a hollow shaft 10 
is rotatably mounted by means of two ball bearings 11, 12 (FIG. 1). A worm 
gear 13 is secured to the hollow shaft by means of a wedge, this worm gear 
being connected to a drive worm 14 which is connected to the shaft of the 
motor 7 in a manner not shown in the drawing such that it rotates with the 
shaft. 
The hollow shaft 10 is slipped over the end of the drive shaft 1 and 
rotatably mounted around this shaft. For this purpose a first ball bearing 
15 is provided within the gear unit at the end of the shaft. A second 
bearing position results from a second ball bearing 16, which is disposed 
outside the housing 9 in the illustrated embodiment and the outer ring of 
which is located within a sprocket wheel 17, which is slipped onto the 
part of the hollow shaft 10 projecting beyond the housing 9 by means of a 
sleeve-like shaft 18. The sprocket wheel and hollow shaft are connected 
with each other by a wedge 19 so as to be secured against relative 
rotation. 
The drive shaft 1 bears, immediately adjacent to the sprocket wheel 17, a 
sprocket wheel 20 which is fixed to the drive shaft by a wedge 21 so as to 
be secured against rotation relative to the drive shaft. The sprocket 
wheels 17 and 20 have the same diameter and the same tooth pitch. 
Drive units of the type described are--as mentioned--disposed on both sides 
of the shaft so that pairs of sprockets formed by the sprocket wheels 17 
and 20 are provided on both end portions of the shaft. A roller chain 22 
can be laid over the two sprocket wheels of either such pair. This 
connects the two sprocket wheels 17 and 20 with each other so as to secure 
them against relative rotation. In the embodiment illustrated in FIG. 1 
the chain is a so-called duplex chain, i.e. a chain which has two rollers 
next to each other on the same pin, the two rollers being separated from 
each other by stay pins. The rollers disposed next to each other engage in 
the recesses between the teeth of the adjacent sprocket wheels. 
Whereas the one sprocket wheel pair couples the hollow shaft and the drive 
shaft via the chain 22 such that they are secured against relative 
rotation, the adjacent sprocket wheels on the opposite side of the shaft 
remain unconnected so that the drive shaft may be freely rotated relative 
to the hollow shaft. 
The entire drive is, therefore, in this case undertaken by a single drive 
unit. It the other drive unit is to be rendered operative it is sufficient 
to remove the chain 22 from the one pair of sprocket wheels and lay it 
over the other pair of sprocket wheels. It may be done, for example, by 
removing a pin from the chain so that this can be opened. 
The connection between the hollow shaft and the drive shaft requires no 
servicing, in particular no greasing. In addition, it is not necessary to 
cover this point of connection by a casing so that the point of connection 
is quickly and easily accessible when necessary. The change-over from one 
drive unit to the other may therefore take place, with the construction 
according to the invention, extremely quickly and without difficulty. 
As shown in particular in FIG. 2 the housing 9 bears an arm 23 projecting 
approximately radially of the drive shaft 1; this arm abuts at one end on 
a pressure spring 24. The pressure spring abuts with its other end on a 
stationary part of the machine 25 and extends thereby substantially at 
right angles to arm 23 (FIG. 2). A limit switch is also connected to the 
stationary machine part 25, this switch being operatively connected to a 
control element 27 of the limit switch 26. 
When the associated gear unit is coupled with the drive shaft such that it 
is secured against rotation relative to the drive shaft, the gear unit 
rotates according to the torque transmitted to the drive shaft, contrary 
to the effect to the pressure spring 24, more or less at the end of the 
drive shaft. When a certain torque is exceeded, this rotation will be so 
great that the control element 27 of the limit switch 26 will be activated 
and shut down the motor. The entire arrangement, which may be designated 
as a resilient torque support, therefore serves as a protection against 
overloading. 
The construction of this arrangement is very simple and is made possible in 
that a gear unit is used which is slightly rotatable about the axis of the 
drive shaft. 
A similar arrangement may be provided for the other drive unit. 
In order to prevent the drive unit not coupled with the drive shaft 
rotating during operation due to the effect of residual friction between 
hollow shaft and drive shaft a stop 28 which is secured to the machine can 
be provided, which may, for example, engage on the arm 23 (FIG. 2). 
The arrangement according to the invention of two slip-on drive units on 
opposite shaft ends also has the advantage that during operation of the 
drive shaft the reserve drive unit not required for the moment can be 
serviced. This does not require any interruption of operations. It is also 
an advantage that due to the rotatable mounting of the drive unit on the 
drive shaft a relative displacement of the drive unit on the drive shaft 
in the axial direction can easily take place; aging effects, for example 
of fretting corrosion, which make the removal of the gear unit in the case 
of customary slip-on gear units much more difficult, do not occur in this 
case. 
The coupling of the hollow shaft and the drive shaft such that they do not 
rotate relative to each other is preferably carried out by means of 
sprocket wheels and a chain connecting these. It is, however, also 
possible to achieve this coupling in another way, for example by positive 
connections of two coupling elements or by a connecting link inserted 
through two coupling elements.