Linear drive device

A linear drive device has a linear motor which consists of a piston, an output rod and a control rod. The two rods extend through the two end plates of the motor housing. The working or output rod is designed for the transmission of power to some structure. The control rod cooperates a sensor for positioning. The sensor and also a valve arrangement is integrated in the housing end plate associated with the control rod. The valve arrangement controls flow through pressure fluid duct provided in the housing end plate at the control end for actuating the linear motor.

CROSS REFERENCE TO RELATED APPLICATIONS 
This invention is related to the inventions disclosed in U.S. Ser. No. 
07/389,004, filed Aug. 2, 1989 (now U.S. Pat. No. 4,987,822, issued Jan. 
29, 1991) and U.S. Ser. No. 07/740,444, filed Aug. 5, 1991 (which was a 
Rule 62 continuation of U.S. Ser. No. 07/493,922, filed Mar. 14, 1990). 
BACKGROUND OF THE INVENTION 
The invention relates to a linear drive device comprising a linear motor, 
which has a motor housing with a housing cavity, in which an axially 
displaceable piston separates two working spaces from each other and which 
together with a power output rod and a control rod constitutes a common 
moving drive unit, the two rods being arranged on opposite axial sides of 
the piston and, extending through the respectively associated housing end 
plate, which shuts off the housing cavity at the end thereof, extend out 
of a power output end and a control end of the motor housing, an 
electrically operated actuating device in the form of a valve device 
having a solenoid for effecting the supply and/or discharge of pneumatic 
or hydraulic fluid in relation to at least one working space for actuating 
the linear motor, and at least one sensor for responding to certain 
positions of translation of the control rod, the valve device, solenoid 
and the sensor being arranged adjacent to the control end of the linear 
motor. 
In the case of a linear drive device of this type as for instance described 
in European patent publication 10 355 179 A, the linear motor is more 
particularly designed in the form of a piston and cylinder unit, whose 
piston rod represents the actuating or output rod, which is able to be 
connected with a component to be moved or with some other part to be acted 
upon. In this case the control rod together with at least one sensor is 
responsible for producing control signals on the basis of which the valve 
arrangement is operated, which is responsible for the distribution of 
working fluid to the working spaces of the linear motor. A control device 
is provided for processing the control signals and the operation of the 
valve arrangement, such control device generally being mounted externally. 
This known linear drive device already has the advantage that the main 
components are joined together as a unit able to be handled as such. 
However, the space requirement for this device is still excessive for many 
applications more particularly owning to the valve arrangement and sensors 
placed to the side of the control rod. Furthermore a flange-mounted 
holding structure is necessary at one end in order to attach these parts 
securely and in a manner free of vibration. A further point to be 
considered is that the assembly of the valve arrangement and of the 
sensors on the holding structure is slow, because free, exposed working 
fluid lines and control lines are still necessary. 
SHORT SUMMARY OF THE INVENTION 
One object of the present invention is to provide a linear drive device of 
the type initially mentioned which while having a compact design is 
characterized by enhanced economy in the space requirement. 
A still further object of the present invention is to provide such a linear 
drive system which is simpler to mount and fit. 
In order to achieve these and/or other objects, the valve arrangement and 
the sensor are carried on the housing end plate adjacent to the control 
end, the valve arrangement being seated in at least one receiving well in 
the housing end plate adjacent to the control end, in the interior of the 
housing end plate adjacent to the control end fluid ducts are formed which 
connect fluid connection means, arranged on the outside of the housing end 
plate with at least one of the working spaces which are controlled by the 
valve arrangement. On the outer side of the housing end plate at the 
control end first electrical connection means are provided which, via 
electrical lines extending in the interior of the housing end plate, are 
connected with the actuating device of the valve arrangement. On the outer 
side of the housing end plate at the control end a second electrical 
connection means is provided which is connected via control lines with the 
sensor. 
In this manner the invention provides a linear drive device wherein both 
the sensors and also the valve device are practically integrated in the 
housing end plate at the control end so that external hoses and cables are 
generally unnecessary. The result is a compact component, the valve device 
assuming a position within the housing end plate whereat it is protected 
and wherein it is not responsible for any widening of the conventional 
overall size of the unit. The connection of a control device and of a 
pressure fluid supply is very simple and may be performed by a connection 
with the fluid power and electrical connection means in a time-saving 
manner. On the valve arrangement itself it is unnecessary to connect any 
hose pipe, something that completely excludes the danger of confusion of 
connections. Lastly, complex holding structures are no longer necessary, 
because the valve arrangement and the sensors are arranged on the linear 
motor. All in all, the result is an extremely slim external configuration 
without any broadening out in excess of ISO Standard dimensions. 
Preferably the valve arrangement comprises two valves, which are 
respectively in the form of 3/2 way valves and are respectively 
responsible for the supply and discharge of working fluid in relation to 
one of the two working spaces. 
It is furthermore an advantage if the control lines of the sensors are 
essentially and preferably completely within the interior of the housing 
end plate at the control end so that there is no danger of damage. 
The connection means provided on the housing end plate are expediently 
joined together with each other as multiple connection devices which are 
termed so-called multipole connection means. They are preferably designed 
in the form of plug and socket connection means so that instant make and 
break of the connection is possible. 
If on the housing end plate at the control end two sensors are provided for 
cooperation with the control rod, on the one hand, and with the piston 
rod, on the other hand, position detection means, as for instance an 
electrical one, for sensing the position of the drive unit in both 
directions of the stroke may be employed. Furthermore in order to ensure 
that a switching spur of the control rod always assumes the correct 
position relation to the associated sensor, it is preferred to provide the 
control rod with a non-circular and, more particularly, a rectangular 
cross section so that it is prevented from twisting about its axis. 
It is furthermore preferred to provide abutment means on the housing end 
plate at the control end in order to limit the stroke of the drive unit, 
which renders possible a very sensitive fine adjustment as for instance 
down to exactly 1/100 mm. 
Furthermore together with a suitable control device it is possible for the 
linear drive device to be operated with a stroke speed which is up 30% 
higher than in known drive equipment if the supply of working fluid is 
suitably regulated by operation of the valves. 
Further advantageous developments and convenient forms of the invention 
will be gathered from the following detailed account of one embodiment 
thereof in conjunction with the accompanying drawings.

DETAILED ACCOUNT OF WORKING EMBODIMENTS OF THE INVENTION 
All figures are purely diagrammatic. The linear drive device generally 
referenced 1 in the figures possesses as its main component a linear motor 
2, which is designed in the form of a piston and cylinder unit. The linear 
motor 2 has a motor housing 3 with a tubular portion 8, in which a housing 
space is formed, which functions as the bore receiving a piston 5 adapted 
to run axially therein. The ends of the motor housing 3 are shut off by 
two housing end plates 6 and 7, which constitute the axial limitation of 
the housing space 4 as well. They may optionally be make integrally with 
the tubular section 8, but in the working embodiment they are designed as 
a separate component. 
Using seals, not illustrated in detail, the piston 5 divides the housing 
space 2 into two working spaces 10 and 11. Both of them are able to be 
vented or pressurized with a pressure fluid such as a compressed air, for 
which purpose there are ducts to be described below and which as shown in 
FIG. 3 open at 12 and 13 into the two working spaces 10 and 11. 
One side of the piston 5 is connected with a drive or output rod 9, which 
extends in the axial direction 16 which coincides with the direction of 
displacement of the piston 5 and extends to the outside at the end 17 of 
the drive assembly after passing through the associated housing end plate 
7 and a seal therein. The outwardly extending working section 18 
constitute the power transmission or power output member which is able to 
be connected with any desired structure. 
The opposite side of the piston 5 bears a control rod 19 which is coaxially 
mounted in relation to the output rod 9, which extends through the housing 
end plate 6 associated with it and in an opening 20 in the end plate to 
the outside and at the control end 21, opposite to the power output end 7. 
The output rod 9, the piston 5 and the control rod 19 are collectively 
referred to as a jointly moving device unit 22. 
The control rod 19 is adapted to cooperate with at least one sensor 23, 
which responds at certain positions of displacement of the drive unit 22 
so that practically the respective position of displacement may be 
detected or ascertained. There are control lines 24 for conducting the 
signals produced to a diagrammatically illustrated control device 25, 
which for its part is able to operate a valve arrangement 26 in a manner 
dependent on such signals, which in the working embodiment shown consists 
of two valves 27, which are preferably in the form of 3/2 way valves. The 
valves 27 possess an actuating device 28, which is only diagrammatically 
illustrated, such as an electrically operated solenoid which may be 
operated to regulate the supply of working fluid to an/or discharged from 
the two working spaces 10 and 11 in order to operate the linear motor by 
causing the drive unit 22 to perform an axially directed movement. 
The openings 12 and 13 are connected with the pressure ducts 29 which 
extend in the housing end plate 6 at the control end. More specifically, 
in the embodiment of the invention for each valve 27 in the housing end 
plate 6 at the control end there is a feed duct 33 and 33', a venting duct 
34 and 34' and a power duct 35 and 35'. Internally the two feed ducts 33 
and 33' and the two venting ducts 34 and 34' are each connected with each 
other at one end. Each pair 33 and 33' and, respectively, 34 and 34' of 
ducts produced in this manner is furthermore connected with a fluid 
connection means 38 and 38', which is arranged adjacent to the outer 
surface of the housing end plate 6 at the control end. Furthermore it is 
possible for branch ducts 37 to be provided in the housing end plate 6 at 
the control end, which function to connect the respective pair of ducts 
with the respective connection means 38 and 38'. 
One of the power ducts 35 opens at one end at 12 with the working space 10 
at the control end. The other power duct 35' has its one end connected to 
a supply duct 42, which runs in the wall 41 of the tubular portion 8 
axially to the side along the housing space 4 towards the housing end 
plate 7 at the control end in order to finally open at 13 into the working 
space 11. 
The ducts 33, 34, 35 and respectively 33', 34' and 35' associated with the 
respective valve 27 have their respectively other ends opening at mounting 
emplacements 43 for component, the openings being illustrated in FIG. 3 at 
44. At these mounting emplacements a respective one of the valves 27 is so 
detachably mounted that the internal valve ducts are connected in a known 
manner with the associated openings 44. The mounting emplacements 43 are 
in this case part of receiving wells 48 of which for each valve one is 
placed in the housing end plate 6 at the control end and in which the 
valve 27 are mounted, preferably so that they are completely sunk 
thereinto. This leads to a compact arrangement with a substantially smooth 
surface and no substantial projecting parts. 
In the embodiment of the invention the two receiving wells 48 are spread 
out around the periphery of the control rod 19 with a spacing in the 
circumferential direction of the housing end plate 6 at the control end 
and in relation to the longitudinal axis 16 are diametrically opposite to 
each other. In this respect it is a question of cubic receiving wells or 
recesses 48, which are designed in the form of pockets and whose openings 
are oriented radially outward. At the axial end and at the periphery the 
receiving wells 48 are therefore preferably limited by the material of the 
housing end plate 6. The assembly of the valve 27 is preferably performed 
as part of a plugging in operation. 
The housing end plates 6 and 7 preferably have a rectangular cross section 
and, in the case of the invention, are square in outline. The two 
receiving wells 48 are in this case preferably located adjacent to 
opposite, parallel side surfaces and preferably adjacent to the respective 
midpoint of the side as shown in FIG. 1. 
Furthermore first electrical connection means 50 are provided on the outer 
side of the housing end plate 6 at the control end, such means being 
connected via electrical lines 40, running inside the housing end plate 6 
at the control end, with the actuating means 28 of the two valves 27. 
Furthermore, in addition to the above noted sensor 23, there is a further 
sensor 23' held on the housing end plate 6 at the control end and which 
cooperates with the piston 5 for excitation thereof. Both the sensors 23 
and 23' are connected with the above noted control lines 24, which are 
preferably arranged to run inside the housing end plate 6 at the control 
end and lead to second electrical connection means 51 arranged on the 
outside of the housing end plate. 
The housing end plate 6 at the control end therefore constitutes a highly 
integrated component, on which both the valve arrangement 26 and also the 
sensors 23 and 23' and the fluid and electrical connection means 38, 38' 
and 50, 51' are arranged. 
The electrical lines 40 and the control lines 24 may be designed in the 
form of printed wiring. In the embodiment of the invention, cables are 
utilized which are laid in suitable ducts and recesses in the housing end 
plate. 
The fluid connection means 38 and 38' render possible the connection of 
external fluid connection members 53 such as pressure fluid lines or 
pressure fluid hose in order to produce a connection with a pressure fluid 
source P and/or to a point R, to which air from a working space is to be 
vented. The electrical connection means 50 and 51 make possible the 
connection of electrical connection members such as cables 54 and the 
like, which in the working embodiment lead to control means 25. 
Since in the case of the working embodiment all connection means 38 and 38' 
50 and 51 are designed in the form of plugs and sockets therefor, it is 
possible for the connection members to be connected or terminated by a 
plugging action. The associated connection ends of the connection members 
53 and 54 are for this purpose provide with plugs 55 complementary to the 
connection means of the housing end plates. In order to ensure that it is 
unnecessary for each supply member to be connected separately, the fluid 
connection means 38 and 38' are combined together to form a multiple fluid 
power connection device 56 and the electrical connections 50 and 51 are 
combined together to form an electrical multiple connection device 57, 
which connection devices are termed so-called multipole connection 
devices. In the case of the plugs, suitable multiple plugs are utilized. 
As regards the electrical connection means it is furthermore advisable to 
arrange the first and the second electrical connection means 50 and 51 in 
separate groups of multiple connection means. 
Of the fluid power connection means 38 and 38' one is provided for the 
pressure fluid source P and the other is provided for the discharge point 
R. However it will be clear that in case of need it is possible to do 
without a connection means 38' joined with a discharge point R, if venting 
is able to take place directly into the surroundings of the linear drive 
assembly 1. In this case only one external supply duct is necessary so 
that the design only has a minimum amount of hose. 
The two sensors 23 and 23' are in the working embodiment essentially in the 
form of rods or pins and each have a threaded section with which they are 
screwed into the threaded holes 59 and 59' in the housing end plate 6 at 
the control end and which extend in the axial direction 16. For the sensor 
23 in cooperation with the control rod 19 the threaded hole 59 is 
preferably a blind hole extending in from the control end 21 and the 
sensor 23 screwed into the same has its detection or signal part 60 
extending to a larger or smaller extent past the axial end surface of the 
housing end plate 6 at the control end. 
The control rod 19 has, on its part outside the motor housing 3, a radially 
projecting switching spur 61, which is moved with the control rod 19 and 
into its displacement path the detection part 60 preferably extends. The 
detection part 60 and the switching spur 61 are preferably in axial 
alignment with each other. If during operation of the assembly the 
switching spur 61 approaches the detection part 60 by a certain amount, 
the sensor 23 will respond. 
In order to economize in space, the switching spur 61 is preferably not in 
the form of a flange or a ring but only in the form of a project lug or a 
pin. In order to nevertheless ensure a correct position in relation to the 
sensor 23, the control rod 19 has a non-circular cross section, in the 
present working embodiment, a square one. The shape of the opening 20 in 
the end plate is complementary so that a simple way of prevention relative 
twist is provided. 
For the sensor 23' cooperating with the piston 5 there is a threaded hole 
59' extending axially through the housing end plate 6 at the control end 
and into which the sensor 23' is screwed from the outside. Its detection 
point 60 is arranged on the side in front of the piston 5 so that 
practically the two sensors 23 and 23' are associated with opposite axial 
sides of the housing end plate 6 at the control end. Preferably however 
the detection part 60 is sunk into the interior of the threaded hole 59' 
so that there is no risk of impact of the piston 5 against it. If the 
sensor 23 is also provided with abutment means or other abutment means are 
provided, it is possible naturally for it to extend into the interior of 
the working space 10. 
The outer sensor 23 is in the working embodiment provided with an abutment 
means 65 in order to limit the stroke of the drive unit. This abutment 
means 65 practically constitutes a subassembly with the sensor 23 and for 
this purpose is constituted by an abutment sleeve, which, provided with an 
internal screw thread, is so screwed on the free end of the sensor 23 that 
the detection part 60 is sunk into the sleeve recess. Accordingly if the 
piston 5 moves towards the working end 17, the switching spur 61 will as 
part of this movement run up against the end of the abutment means 65, the 
sensor 23 then preferably responding. 
It will be clear that optional abutment means may be arranged separately 
alongside the sensors on the housing end plate 6. 
Owing to the possibility of axial displacement of the sensors 23 and 23' 
and/or of the abutment means 65, it is possible to very exactly set the 
desired ends of the strokes. In the illustrated working embodiment of the 
invention, it is only necessary to screw the sensors in the threaded hole 
or to screw the sleeve-like abutment means 65 onto the associated sensor. 
The connection means 38, 38', 50 and 41 are preferably arranged on the 
control side of the end plate 6 at the control end. In this case connected 
members 53 and 54 do not extend radially clear of the other parts so that 
a slim and compact structure is provided. The two sensors 23 and 23' and, 
respectively, the associated threaded holes 59 and 59' are preferably 
arranged radially in succession with respect to the longitudinal axis 16, 
while in the axil direction as seen in FIG. 1 they are preferably aligned 
on a longitudinal median axis of the housing end plate 6 with a square 
outline. On the same line the fluid power connection means 38 and 38' are 
preferably also arranged, but however preferably diametrically opposite to 
each other with respect to the longitudinal axis 16. The receiving wells 
48 or recesses are preferably arranged with bilateral symmetry with 
respect to this connecting line to the left and to the right. Furthermore, 
and as shown in FIG. 1, the electrical connection means 50 and 51 are 
preferably arranged in a corner part of the housing end plate 6 at the 
control end. 
Operation of the device is now possible in such a manner that the two 
valves 27 are switched alternatingly via the control device 25 so that the 
drive unit 22 performs a reciprocating movement. Reversal of the stroke 
direction takes place using the sensors 23 and 23', which on the approach 
of the piston 5 or, respectively, of the switching spur 61 produce a 
signal which is passed to the control device 25, which then 
correspondingly reverses the actuating device of means 28. 
Owing to the extremely short fluid power paths there is a great saving in 
compressed air, in the case of pneumatic equipment of up to 20%. 
Furthermore the response behavior is favorably affected thereby. The low 
compressed air requirement renders possible a further saving in costs, 
since only very small valve dimensions are necessary. The sensor control 
system is very favorable in price since it is possible to do without 
solenoids. By suitable programing of the control device 25 it is possible 
to operate the valves in an extremely adaptable manner such as, for 
instance, a manner in which the drive unit is run at a high speed, while 
on reaching the end of a stroke there is a reduction of the speed for a 
very short part of the stroke. 
At 66 it is possible to provide a protective boot at shown in broken lines, 
which on the control end my be mounted on the housing end plate 6 in order 
to accommodate members arranged here without danger to the operator. The 
annular portion 8 is expediently designed with a non-circular form, for 
instance square, like the housing end plates 6 and 7.