Monitoring apparatus for a transporting system

A transporting system includes a conveyor; a workpiece carrier adapted to be advanced by the conveyor; and a monitoring apparatus for monitoring a presence or absence of the workpiece carrier in a predetermined zone of the conveyor. The monitoring apparatus has a switching element supported adjacent the conveyor and projecting at least partially into a path of the conveyor; and an arrangement for actuating the switching element independently of a direction of conveyance of the workpiece carrier.

CROSS REFERENCE TO RELATED APPLICATION 
This application claims the priority of German Application No. 196 16 696.9 
filed Apr. 27, 1996, which is incorporated herein by reference. 
BACKGROUND OF THE INVENTION 
This invention relates to a monitoring apparatus of a transport system 
which has a conveyor for a workpiece carrier adapted to accommodate 
components or component groups. The monitoring apparatus serves for 
determining the absence or presence of the workpiece carrier in a region 
of the conveyor. 
The above-outlined conventional monitoring apparatus is used particularly 
in a transporting system in which an incoming and an outgoing conveyor 
abut one another at right angles and at the transfer location means are 
provided for detecting the presence or absence of the workpiece carrier. 
At the transfer location a first signal transmitter of the monitoring 
apparatus is arranged which responds to a collision of a workpiece carrier 
with a stationary stop. The first signal transmitter is positioned at the 
transfer location. As long as such a signal is present, a separating 
element which is situated upstream of the transfer location as viewed in 
the conveying direction is in a stop position so that further workpiece 
carriers are prevented access to the transfer location. As soon as the 
workpiece carrier is fed into the transfer location, the first signal 
transmitter is deactivated. At the same time, a second signal transmitter 
of the monitoring apparatus is activated which monitors the departure of 
the workpiece carrier from the transfer location. As long as the second 
signal transmitter is active, the separating element continues to remain 
in a stop position. The separating element is switched into a let-through 
position only after the workpiece carrier has completely left the transfer 
location and the first signal transmitter and the second signal 
transmitter no longer detect the presence of the workpiece carrier, so 
that a subsequent workpiece carrier again may be moved into the transfer 
location. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an improved monitoring 
apparatus of the above-outlined type having a significantly simplified 
construction. 
This object and others to become apparent as the specification progresses, 
are accomplished by the invention, according to which, briefly stated, the 
transporting system includes a conveyor; a workpiece carrier adapted to be 
advanced by the conveyor; and a monitoring apparatus for monitoring a 
presence or absence of the workpiece carrier in a predetermined zone of 
the conveyor. The monitoring apparatus has a switching element supported 
adjacent the conveyor and projecting at least partially into a path of the 
conveyor; and an arrangement for actuating the switching element 
independently of a direction of conveyance of the workpiece carrier. 
The monitoring apparatus of a transporting system according to the 
invention has thus the advantage over prior art constructions that it is 
feasible to monitor the transfer location with a sole apparatus to 
determine the presence or absence of a workpiece carrier. 
In this manner, the monitoring of the transfer location may be reduced to a 
single signal transmitter whereby significant cost and time saving may 
achieved in the assembly and control of the apparatus. 
The monitoring apparatus which may be actuated independently of the 
conveying direction of the workpiece carrier, may thus detect the presence 
of a workpiece carrier in the transfer location and may also detect its 
departure from the transfer location. Furthermore, the monitoring 
apparatus according to the invention may form, at the same time, a stop 
for the workpiece carrier arriving in the transfer location. The 
monitoring apparatus according to the invention may be positioned 
externally of a transfer location, whereby a zone of the conveyor may be 
monitored. 
According to an advantageous feature of the invention, the monitoring 
device comprises a switching element rotatably and/or linearly 
displaceably guided in a housing in the transporting plane of the 
workpiece carrier. In this manner a simple structural embodiment is 
obtained and a simple operation of the switching element by the workpiece 
carrier is achieved for detecting the presence of a workpiece carrier in 
the zone to be monitored. The switching element remains actuated until the 
workpiece carrier has entirely passed over or left the switching element; 
this makes possible a regional monitoring. 
Further, the switching element of the monitoring apparatus has 
advantageously at least one run-up ramp oriented partially opposite a 
transporting direction of the workpiece carrier. By means of this 
arrangement, a smooth, disturbance-free transport of the workpiece carrier 
is ensured because an edge of the workpiece carrier body oriented in the 
transporting direction first engages the run-up ramp and passes thereover, 
whereby the switching element is movable from a position of rest into a 
switching position for detecting the presence of a workpiece carrier. 
According to a further advantageous feature of the monitoring apparatus 
according to the invention, a resetting means is provided which works 
against the actuating direction of the switching element. In this manner, 
in case of an absence of the workpiece carrier the switching element may 
be moved automatically into a position of rest whereby a signal 
transmitter disposed in the housing of the monitoring apparatus is not 
actuated and the absence of a workpiece carrier may be detected. 
According to a further advantageous feature of the invention a particular 
guidance of the switching element in the housing is provided. Preferably, 
the switching element has two openings which are spaced from the central 
axis of the switching element and extend parallel thereto and which 
receive cylindrical pins that are fixedly secured to the housing. By 
virtue of this arrangement it is feasible to detect a workpiece carrier 
which runs up on the switching element in the operating direction in the 
monitoring range or to detect a workpiece carrier which moves onto the 
switching element transversely to the operating direction. In case of a 
workpiece carrier which is moved transversely to the operating direction 
of the switching element on the transporting path, the switching element, 
by means of the openings which are preferably slots, may execute first a 
slight rotary motion and subsequently may be moved entirely in the 
operating direction into a switching position.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a portion of a transporting system 11 which is part of a 
modular production line. The transporting system has a main circulating 
track, shown in part as a main conveyor 12. The main circulating track 
further has a return transporting portion. Separate, non-illustrated 
deflecting modules are provided at both ends of the supply or main 
conveyor track and the return transporting portion. The main conveyor 12, 
as well as the return transport portion may be formed of several conveyor 
section modules. 
In the present embodiment the transport system 11 is a dual belt conveyor 
where, for example, each section module has its own drive for the conveyor 
belts. It is feasible, however, to utilize other types of transport 
systems. Along the main conveyor 12 a lateral supply section is arranged 
which is associated, for example, with a work station. Such a lateral 
supply section is typically represented by a feed-in module 13 which is 
disposed perpendicularly to the main conveyor 12 and which has a feed-in 
section 14. The main conveyor 12 and the feed-in section 14 form a 
transfer location 16, by means of which a workpiece carrier 21 which was 
deviated into a lateral supply section is fed to the main conveyor 12. The 
transfer location 16 is monitored by a monitoring apparatus 17 which is 
situated externally of an outer conveyor section 18 of the main conveyor 
12, in an exit region 19 of the transfer location 16. By virtue of such an 
arrangement of the monitoring apparatus 17 relative to the transfer 
location 16, it is sufficient to utilize a single monitoring apparatus 17 
to determine a presence or an absence of a workpiece carrier 21 at the 
transfer location 16, as it will be described in detail below. 
Turning to FIG. 2, the monitoring apparatus 17 has a housing 22 which is 
secured to the outer conveyor section 18 by means of a securing device 23 
which preferably is a hammer head screw securable in a groove 24 of a 
profile element 26 of the outer conveyor section 18. The workpiece carrier 
21 is guided on a workpiece carrier rail 27 which is clipped on a frontal 
side of the profile element 26. The workpiece carrier rail 27 has a guide 
strip 28 situated externally of the main conveyor 12 to guide the 
workpiece carrier 21 in the main conveyor 12. A non-illustrated inner 
conveyor section is similarly structured. A transporting belt 29 runs on 
the workpiece carrier rail 27 and moves the workpiece carrier 21 in the 
transporting direction. The workpiece carrier 21 has a foot 31 supported 
on the transport belt 29. The foot 31 is adjoined by a shoulder 32 of the 
workpiece carrier 21 whereby an external edge 33 is formed which partially 
surrounds the guide strip 28. By means of the external edge 33 of the 
workpiece carrier 21 a switching element 34 of the monitoring apparatus 17 
is actuated. 
The switching element 34 is floatingly (slidably) supported in a guide 36 
of the housing 22 and may be moved out from a position of rest 38 shown in 
solid lines in the direction of the arrow 37 parallel to a transporting 
plane into a switching position 41 shown in dash-dot lines. 
The housing 22 is a one-piece component made of a synthetic material. The 
guide 36 is a cross-sectionally rectangular groove which extends over the 
length of the housing 22 as shown in FIG. 3. The switching element 34 is a 
slide or plunger made of a synthetic material. 
The switching element 34 has a central axis 42 parallel to the direction 37 
and slots 43 spaced from the axis 42. The length of the slots 43 
corresponds to at least one switching stroke of the switching element 34 
between the position of rest 38 and the switching position 41. The slots 
43 receive respective cylindrical pins 44 which are fixedly secured to the 
housing 22 and which may be inserted freely from above into the housing 
22, ensuring a simple assembly. Between the switching element 34 and a 
rear wall 46 of the guide 36 a resetting means 47 is arranged by means of 
which the switching element 34 may be automatically positioned in the 
position of rest 38 in case of an absence of a workpiece carrier 21. The 
resetting means 47 is preferably a compression spring disposed in an axial 
alignment with the axis 42. It is to be understood, however, that 
elastically yielding spring elements may also be used. 
A signal transmitter 48 is arranged perpendicularly to the direction of 
motion 37 of the switching element 34. The signal transmitter 48 is 
mounted on a housing wall 51 by means of a securing plate 49. The securing 
plate 49 is attached to the housing wall 51 by a screw connection so that 
the distance of the signal transmitter 48 from the switching element 34 is 
adjustable. The switching element 34 has, at its side oriented towards the 
signal transmitter 48, an expediently sprayed-on metal insert 52 which 
operates as a switching means. The signal transmitter 48 may be actuated 
when a small portion of its frontal face, for example, one third thereof, 
is in an overlapping relationship with the metal insert 52 to thus respond 
to the presence of a workpiece carrier 21. 
The signal transmitter 48 is an inductive proximity switch so that in case 
of an excursion of the switching element 34 caused by an edge 33 of the 
workpiece carrier 21, the signal transmitter 48 is actuated and transmits 
a signal to a control device as soon as the signal transmitter 48 is in an 
at least partially overlapping relationship with the metal insert 52 of 
the switching element 34. In the alternative, the signal transmitter may 
be a capacitive, optical or mechanical signal transmitter in which case 
the switching element 34 is adapted to the alternative design of the 
signal transmitter 48. 
The switching element 34 of the monitoring apparatus 17 has run-up ramps 53 
oriented in and against the transporting direction of the workpiece 
carrier 21. By virtue of this arrangement, the monitoring apparatus 17 may 
be universally used independently from the direction of conveyance. 
The switching element 34 is arranged in the position of rest 38 in such a 
manner that a switching face 54 thereof oriented towards the conveyor path 
overlaps at least the guide strip 28. Preferably, the switching face 54 
projects into the transporting path to ensure that an external edge 33 of 
the workpiece carrier 21 actuates the switching face 54. The switching 
stroke of the switching element 34 is expediently 3-7 mm; the switching 
face 54 may project approximately 2 mm beyond the guide strip 28 in the 
transport section. The switching face 54 is at least so wide that the edge 
33 of the workpiece carrier 21 may be actuated independently of its upper 
or lower position into which it is brought by a transversal stroke unit 
58. 
The monitoring apparatus 17 according to the invention may monitor a zone 
19 independently of the direction of conveyance of a workpiece carrier 21. 
Such an operation is described below, for example, for monitoring the 
transfer location 16. For this purpose, the monitoring apparatus 17 is 
positioned externally of an outer conveying section 18 of the main 
conveyor 12 in an outgoing zone 19 of the transfer location 16. The 
monitoring apparatus 17 is further arranged such that its face is oriented 
from a side path toward an outer conveying section 57 of the feed-in path 
14 of the feed-in module 13. The monitoring apparatus 17 extends in the 
conveying direction 61 at least partially over the outer conveyor path 
portion 57. The monitoring apparatus 17 may be coupled with a 
non-illustrated separating element which is arranged upstream of the 
transfer location 16 relative to the main conveyor 12. The separating 
element may be situated at a distance from the main conveyor 12 in front 
of the transfer location 16 to ensure that a workpiece carrier 21, held 
back by a separating element, is positioned at a distance from a workpiece 
carrier 21 situated in the transfer location 16 so that no collision 
between the workpiece carriers may take place. 
In the operational description which follows, it is assumed that a 
separating element is arranged in the main conveyor 12. The separating 
element is moved into a stopping position so that no further workpiece 
carrier 21 may be fed into the transfer location 16 because a workpiece 
carrier 21 present in the feed-in module 13 is to be advanced to the main 
conveyor 12. 
After the workpiece carrier 21 has been moved into the transfer location 
16, such a position is detected by the monitoring apparatus 17. At the 
same time, the monitoring apparatus 17 serves as a stop so that the 
workpiece carrier 21 is arrested in its transport motion after it has been 
fed into the transfer location 16. Thus, the monitoring apparatus 17 
performs a dual function as it monitors the transfer location 16. First, 
it serves as a stop and second, it recognizes whether a workpiece carrier 
21 is present in the transfer location 16. 
After the workpiece carrier 21 has been detected in the transfer location 
16, the monitoring apparatus 17 transmits a signal to a transverse stroke 
unit 58 which is lowered as a result. After the latter has reached a lower 
position, the workpiece carrier 21 is placed on the main conveyor 12 and 
is moved out of the transfer location 16 in the principal transport 
direction 61. During the feed-out of the workpiece carrier 21 from the 
transfer location 16, an edge 33 of the workpiece carrier 21 engages the 
switching element 34 and holds the same in its switching position 41. By 
virtue of the length of the switching element 34 which extends at least 
with a short section over the outer conveyor portion 57 in the 
transporting direction 61, it may be ensured that the switching element 
34, after the workpiece carrier 21 has been fully moved out of the 
transfer location 16, is shifted from the switching position 41 into the 
position of rest 38 by the resetting means 47 and it detects the absence 
of the workpiece carrier 21 in the transfer location 16. 
In this manner, the transfer location 16 may be monitored by a monitoring 
apparatus 17 which may detect the occurrence when a workpiece carrier 21 
has been moved into the transfer location 16 and thus may monitor the 
presence and the removal of a workpiece carrier 21. 
The monitoring apparatus 17 may also be arranged at additional transfer 
locations which are formed, for example, by a main conveyor with a 
feed-out module, a feed-out module and a side conveyor or a side conveyor 
and a feed-in module. 
In the alternative, the transfer location 16 may have a monitoring 
apparatus 17 without being associated with a separating element. 
As another alternative or in addition, a monitoring apparatus 17 may 
monitor the presence of a workpiece carrier 21 in the region of a conveyor 
section of the conveyor system. In such an application, the extent of the 
monitored zone is determined by twice the length of an edge 33 of the 
workpiece carrier 21 and the length of a switching face 54 which is part 
of the switching element 34 and which extends parallel to the conveying 
direction. The switching element 34 has a run-up ramp 53 to ensure a 
simple actuation of the switching element 34 upon arrival of the workpiece 
carrier 21 into the zone to be monitored. In this manner, the switching 
element 34 may be first exposed to a turning motion which, as a function 
of the fine adjustment of a signal transmitter 48 relative to the 
switching means 52 of the switching element 34 may already detect the 
presence of a workpiece carrier 21. Thereafter the switching element 34 is 
guided substantially parallel to the edge 33 of the workpiece carrier 21 
into the switching position 41 and is maintained therein. 
By so designing a left and right-hand end of the switching element 34 that 
it at least partially extends into the conveyor, the monitoring apparatus 
17 may find application independently of the conveying direction. 
In the alternative, the switching element 34 may be moved by other 
arrangements from its position of rest 38 into its switching position 41 
to actuate a signal transmitter 48. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations, and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.