Pressure driven rotary drive

A hydraulically operated rotary drive includes a housing which is closed in hydraulically tight manner by flat covers and can be connected to a source of pressure fluid, a rotatable shaft extending through the covers out of the housing and a belt which is arranged at least in part within the housing with the formation of movable pressure chambers and is operatively connected to the shaft. In order to create a rotary drive which permits any desired extension to external structural groups as well as a modular extension to a plurality of rotary drives, it is proposed that axially extending channels (2, 2') for receiving and forwarding the pressure fluid to the pressure chambers and electrical connections be integrated within the shaft and that the shaft (3) be provided on both axial ends with coupling elements for the coupling outside the housing of mechanical and/or electrical attachment modules which can be coupled to the rotary movement.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a hydraulically operated rotary drive 
including a housing which can be connected to a source of pressure fluid, 
a rotatable shaft, and a belt which is arranged at least partially within 
the housing with the formation of movable pressure chambers and is 
functionally connected to the shaft. 
2. Description of the Related Art 
A hydraulically operated rotary drive of this type is known from U.S. Pat. 
No. 4,838,148. In that known rotary drive, a flexible belt is arranged 
within a housing having a hollow space and forms movable pressure chambers 
within the housing. These movable pressure chambers are formed by the 
provision of rollers or roller-shaped bodies within the housing, over 
which the belt is passed, forming at least one open loop. The movable 
pressure chambers 14 are constructed and operate in the manner disclosed, 
for example, in above-mentioned U.S. Pat. No. 4,838,148. Thus, the shaft 3 
is rotated by the belt 15 when pressure fluid is admitted to one of the 
chambers 14. 
The belt is movable within the hollow space in such a manner that by its 
revolving it changes the open region of the loop which forms the pressure 
chambers. This change is effected in the final analysis by the pressure 
fluid introduced into the movable pressure chambers. The two outer edges 
of the belt rest in the housing or in the hollow space in such a manner 
that, on the one hand, it is still readily movable while, on the other 
hand, it seals in hydraulically tight manner. The change or movement of 
the belt effected by the impact of pressure with the formation of the 
aforementioned open loop results, upon travel over the rotatable roller 
arranged within the housing, in a rotary movement which can be tapped off. 
This rotary movement is conducted outward via a shaft. This known 
development has the disadvantage that it cannot readily be extended to 
mechanical or mechanico-electrical structural groups. The difficulty in 
such external extension is not solely the mechanical coupling but also the 
effecting of electrical connections and connections of pressure fluid from 
one structural part or module to the other. 
SUMMARY OF THE INVENTION 
The object of the present invention is therefore, proceeding from this 
prior art, to create a rotary drive which permits extension as desired to 
external structural components as well as modular extension to a plurality 
of rotary drives. 
This object is achieved in accordance with the invention in a hydraulically 
operated rotary drive of this type by providing channels integrated within 
the shaft extending in axial direction for receiving and further 
conducting the pressure fluid to the pressure chambers and for electric 
lines. The shaft is provided on both axial ends thereof with coupling 
elements for externally coupling thereto mechanical and/or electrical 
attachment modules for rotation with the shaft. 
The advantages of the hydraulically operated rotary drive proposed by the 
invention result from the suitable adaptation to each other of different 
features which, as a whole, permit simple modular extension of the rotary 
drive to external structural groups or modules. The integrated passage of 
the pressure fluid and of the electric lines is particularly advantageous. 
The integration of the pressure-fluid channels in the shaft of the rotary 
drive, as well as the integrating of the switch valves and servovalves in 
one of the covers, leads to a compact construction. In order now suitably 
to connect the channels conducting pressure fluid which are arranged 
integrated in the shaft to the switch valves and the outwardly extending 
pressure-fluid connections in suitable manner, the shaft is provided, in 
at least one of the cover regions, with holes which extend radially out of 
the shaft and are connected in gas-tight manner with the channels 
conducting the pressure fluid. In order furthermore to connect these holes 
in gas-tight manner with the switch valves and pressure-fluid connections, 
circumferential grooves are provided on the shaft, they being connected in 
gas-tight manner with the channels conducting the pressure fluid. These 
grooves, in their turn, are connected in gas-tight manner via integrated 
channels with the switch valves and with pressure-fluid connections which 
extend towards the outside. In order to obtain the desired tightness, the 
shaft is furthermore provided with a plurality of annular depressions 
which are axially offset from the grooves and into which sealing rings for 
the sealing off of the grooves are arranged. Thus, in this embodiment, 
despite the rotation of the shaft, a suitably tight hydraulic connection 
is obtained in particularly advantageous manner between the stationary 
cover and the connections and switch valves integrated therein and the 
rotatable shaft which contains the channels. 
The servovalves integrated in the cover serve in a simple and compact 
construction for the action of pressure fluid on the pressure chambers 
formed by the belt within the housing. 
In order to obtain a high torque which can be tapped off from the outside, 
a plurality of rotary drives can be connected to each other. For this 
also, the developments in accordance with the invention are extremely 
advantageous since the channels which conduct the pressure fluid and 
electric lines are integrated in the shaft and possibly even connected 
from one rotary drive to the other. In connection herewith, it is 
furthermore advantageous to develop the coupling elements on the axial 
ends of the outward extending shaft as driver connections in accordance 
with the tongue-and-groove principle. Thus, by this development, any type 
of external coupling is prepared for and therefore can be effected 
rapidly. It is furthermore advantageous here to provide the rotary drive 
in this modular manner with an angle-of-rotation transmitter which 
converts the exact position of rotation of the shaft of the rotary drive 
into an electric signal, as a result of which the electric line can be 
passed through the shaft here in a particularly simple manner. 
Furthermore, the rotary drive can, as proposed in the invention, be 
expanded by a brake module in order, for instance, to assure a dependable 
rotational positioning upon rapid rotary movements or even to obtain a 
gripping movement in precise position upon use of a gripper element. In 
such case, the brake can furthermore relieve the rotary drive in the 
manner that, in the end position of the gripper, the gripping pressure of 
the gripper elements can be obtained not by the action of pressure fluid 
in the rotary drive but by the application of the brakes in the brake 
module.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows an embodiment of the invention in which a rotary drive 1 with 
integrated channels 2, 2' in the shaft 3 which conduct pressure-fluid and 
electric lines is shown. Here the actual rotary drive is shown thickened 
in one of the cover regions 4 and provided there with integrated switch 
valves 5 and the corresponding connections to the pressure-fluid lines 2. 
The axially extending channels 2 in the shaft are connected in 
hydraulically tight manner with the corresponding radially extending holes 
6 in the region of the cover 4 which contains the switch valves 5. These 
radially extending holes open into the grooves 7 which are arranged 
annularly in the guide hole 8 which guides the shaft 3 towards the 
outside. Since the shaft 3 is secured against axial displacement, there is 
assurance in every operating situation that the corresponding hole 6, and 
thus the corresponding pressure-fluid channel 7, are in communication in a 
hydraulically tight manner with the intended groove. For the hydraulically 
tight sealing on the one hand of the grooves with respect to each other 
and of the grooves within or outside the housing, the shaft 3 is provided 
with the corresponding annular depressions 9 in which sealing rings are 
arranged. These sealing rings lie in the corresponding depression of the 
shaft and at the same time press against the wall of the guide hole 8 so 
that the corresponding tight closure is produced in this way. In this 
embodiment, both switch valves 5 and servovalves 10 are arranged within 
the cover 4. The servovalves 10 are connected with an outwardly conducted 
pressure-fluid supply connection P and furthermore open at suitable places 
into the movable pressure chambers 14 formed by the belt 15. The switch 
valves 5 are also connected to an outwardly extending pressure-fluid 
supply connection P. 
The pressure-fluid channels 2 in the shaft 3 are in this embodiment led 
outward through a force-transmitting rotary plate 16 arranged on one of 
the ends of the shaft but they can, for instance, simply emerge from the 
shaft and be conducted to another rotary drive which, in its turn, is 
connected on the shaft side to the channels in such a manner that separate 
valves and separate pressure-fluid connections can be dispensed with in 
the case of this further rotary drive. In other words, the pressure-fluid 
channels can be connected in this way from one module to the other. In 
this way, a very simple and compact extension of the rotary drive results. 
In this embodiment, the rotary drive 1 is connected to a brake module 11 
which is coupled to the shaft 3 of the rotary drive 1 via coupling 
elements 20, 21 based on the tongue-and-groove principle. The shaft 
arranged in the brake module 11 is in this connection provided with a disk 
brake 12. Both the shaft of the rotary drive and the shaft of the brake 
module are connected with a widenable channel 2' which extends from one 
module to the other and which, in this example, is intended for the 
passage of electrical lines. The angle-of-rotation transmitter 13, which 
is also coupled via the tongue-and-groove principle above the brake module 
11, operates here as rotary potentiometer, the electric lines for the 
tapping off of the signal being possibly passed through the corresponding 
channel up to the other end of the shaft which emerges from the entire 
structural group. 
FIG. 2 shows an embodiment in which the coupling of two rotary drives 1, 1' 
is shown, the additional rotary drive 1' being adapted to be connected to 
the other rotary drive 1 without separate valves and pressure-fluid 
connections. The feeding of the rotary drive 1' without separate 
connections and valves is effected via the continuing of the channels from 
one module to the other, as already described in connection with FIG. 1. 
By the use of two rotary drives here, twice the torque can be tapped off 
on the outside from the shaft. This torque can be multiplied by arranging 
as many rotary drives as desired one behind the other. The coupling 
elements 20, 21 on the axial ends of the shaft 3, which coupling elements 
are developed in accordance with the tongue-and-groove principle, can be 
clearly noted here. It has been found advantageous in this connection 
that, at each of the rotary drives, the coupling elements 20, 21 at the 
axial ends of the shaft 3 be developed on the one end in pin-like manner 
as tongue-and-groove and that, accordingly, the other axial end of the 
shaft be provided with a hole with the corresponding tongue-and-groove 
contour which receives such a tongue-and-groove pin. In this way, a simple 
arrangement one behind the other is possible. 
FIG. 3 shows an embodiment in which a rotary drive 1 is provided for 
coupling to a gripper 30. In this case, the rotary drive needs no other 
than the previously indicated coupling elements 20, 21 in order to effect 
this. This means, as a whole, that all extension modules are so adapted to 
each other that the coupling elements 20, 21 will always fit each module.