This invention concerns a detection system for detecting operative positions in retaining devices for work pieces, particularly suitable for precisely controlling the functioning of the retaining devices.
For the purposes of this specification, the expression “retaining devices” is understood to mean, without distinction, clamping, positioning and/or centering devices for work pieces.
State of the Art
In different manufacturing fields, in particular in the automotive field, retaining devices are used for clamping, positioning and/or centering work pieces to be assembled or welded to one another.
In general, a retaining device of this type, comprises a box-shaped body for supporting a retaining member which is angularly or linearly movable, depending upon the type of device, between a first operative retaining position and a second operative rest position; the device also comprises control means, such as for example a pneumatic cylinder or a linear electric actuator, operatively connected to the retaining member, by a thrust element movable according to a longitudinal axis.
Devices of this kind are usually installed along complex assembly or processing lines for assembling or processing metal sheets or structural parts of motor vehicles; therefore, in order to correctly function, such devices require precise and perfectly controlled retaining actions, according to the work programs preset for the lines.
It is consequently necessary to accurately control the functioning of the retaining devices, by monitoring the movement of the retaining member, in particular in correspondence with the first operative retaining position and the second operative rest position, the latter being variable for example in relation to the operative requirements of the device or to handling requirements of the work pieces along the line; in this way, appropriate positioning and enabling signals are transmitted to specific control units, thereby allowing a precise control of the entire working cycle.
In order to allow the necessary position controls, different detection systems have been proposed and used, comprising detecting sensors, for example of the optical, inductive or microswitch type, supported in such a way as to detect the aforesaid operative retaining and rest positions of the retaining member.
For example, EP 803331 describes a clamping device of the aforementioned kind for clamping work pieces, comprising a position detecting system, in turn comprising an already known and previously used control cassette, removably secured to the clamping device; in this case, the control cassette is in the form of a structural section supporting a first and a second detecting sensors, which are securable in adjustable positions continuously along the same structural section.
A detection system of this kind offers the advantage of allowing an easy adjustment of the position of one or both the sensors by simply extracting the control cassette from the clamping device and appropriately positioning the sensors along the supporting structural section, in relation to the operative positions of the clamping member to be detected.
However, such sensor position adjustment involves a manual operation of a certain complexity by an operator, which implies the need to stop the production line for a prolonged period of time, in order to allow the adjustment of the numerous retaining devices disposed along the same line.
Moreover, since the detecting sensors can be continuously adjusted along the supporting structural section, there is a possibility that the operator may not correctly position the sensors, resulting in faulty operation of the clamping device.
A different solution has been proposed in EP 1 306 168, which describes a clamping device of the aforementioned kind for clamping work pieces, having a position detecting system comprising a box-shaped casing, removably secured to the clamping device, for supporting a first and a second detecting sensor; in order to enable a precise adjustment of the sensor positions, the box-shaped casing is provided with side walls having a plurality of transversal slots, suitably spaced apart from one another, designed to removably house the sensors.
Such a solution allows to position the sensors in pre-established positions defined at the design stage, in relation to the requirements of the device, thereby defining beforehand and without errors the most suitable positions for the sensors.
However, also in this case a long manual operation is required for removing the supporting box-shaped casing from the clamping device, regulating the position of the sensors, and subsequently repositioning the box-shaped casing; furthermore, there is still a possibility that an operator may erroneously insert the sensors in incorrect positions from among those available.
A further solution has been suggested in EP 1 010 993, which describes a retaining device of the aforementioned kind, having an inner seating for housing a position detecting module which comprises a support casing for supporting a first and a second optical-type detecting sensor, disposed in fixed positions.
In this case, the scope of the patent application is to propose a detecting module whereby it is possible to make reliable detections not subject to disturbances, thanks to the use of optical sensors, nevertheless not new, and a specific conformation of the retaining device close to the sensors. However, it does not deal in any way with the problem of adjusting the position of the sensors, and consequently does not offer any solution to the problem of detecting different operative retaining or rest positions of the retaining member of a retaining device.
The main object of this invention is to provide a detection system for detecting operative positions in a device for retaining work pieces, whereby it is possible to accurately detect different operative positions of the retaining member of the device, and at the same time eliminate any manual operation aimed to modify the configuration or the sensor positioning in the same detection system.
A further object of this invention is to provide a detection system of the aforementioned kind for detecting operative positions, whereby it is possible to detect different operative positions of the retaining member, corresponding to different conditions of use or control of the retaining device, by simply operating suitable means for controlling the functioning of the same detection system, or by mere self-learning of an electronic control unit of the system.
The above can be achieved by means of a system for detecting operative positions in a retaining device for work pieces, in which the retaining device comprises a box-shaped body for supporting a movable retaining member, and drive means operatively connected to the retaining member by a thrust element movable according to a longitudinal axis, the detection system comprising:
These and further features according to this invention, will be more clearly evident from the following description with reference to the accompanying drawings, in which:
The general features of this invention will be illustrated hereunder by means of several exemplificative embodiments.
The clamping device 10 also comprises drive means 13, for example a pneumatic cylinder, an electric cylinder or other suitable linear actuator, operatively connected to the retaining member 12 by a thrust element 14, movable according to a longitudinal axis, and a per se known toggle-lever mechanism 15.
The clamping device 10 shown comprises a detection system 16 for detecting operative positions according to this invention, illustrated in greater detail in the figures from 3 to 8, which in turn comprises an elongated support member 17 for supporting a plurality of detecting sensors 18, 1A-8A, for detecting the position of the thrust element 14.
In particular, the support member 17 is secured to the box-shaped body 11, for example, as illustrated in
The detecting sensors 18, 1A-8A arranged on the support member 17, are spaced apart from one another and aligned in the longitudinal direction of the same support member 17, in order to allow the detection of different positions of the thrust element 14.
Preferentially, the elongated member 17 supporting the sensors 18, 1A-8A, is inserted in the box-shaped body 11 of the retaining device 10 in an inner seating 19, communicating with the outside through a side opening 20 in the box-shaped body 11, which can be tightly closed by a cover 21, removably secured to the box-shaped body 11, the cover 21 being preferentially provided with an appropriate sealing gasket 21′.
The detecting sensors 18, 1A-8A, can detect any suitable means, for example a protrusion or a tab 14′ provided on a side of the thrust element 14, in order to emit enabling signals for controlling the operation of the device.
The detecting system 16 comprises control means for controlling the detecting sensors 18, 1A-8A, in turn comprising means for activating or selectively rendering operative at least one of the sensors 18, 1A-8A, of the plurality of sensors 18, 1A-8A provided, in relation to at least one pre-established operative position to be detected of the retaining member 12.
In particular, the activating means comprise an electronic control unit 22 operatively connected to all the sensors 18, 1A-8A, which is suitably programmed and preset to activate the selected detecting sensor 18, 1A-8A.
In the case of the illustrated clamping device 10, the retaining member 12 can move between a fixed operative position for retaining or clamping a work piece, and an operative position of rest or for releasing the work piece which conversely can be varied, for example by mechanical stop devices or by a suitable programming of an electronic control unit for controlling the linear actuator, in relation to operative requirements or to the handling of work pieces along the production line in which the clamping device can be mounted.
Therefore, in this case the plurality of detecting sensors 18, 1A-8A, comprises only one detecting sensor 18 for detecting the fixed retaining position of the retaining member 12, and a plurality of detecting sensors 1A-8A for detecting the rest position of the retaining member 12, the sensors 1A-8A being selectively activated, so as to be able to accurately detect the each time preset rest position for the retaining member 12.
It cannot be excluded however that several sensors 18 can be provided for detecting the retaining position of the retaining member 12, whenever this is also variable in relation to operating requirements, and that several sensors 18 can be provided for detecting the retaining position of the retaining member 12 and only one sensor 1A for detecting the rest position of the retaining member 12.
Preferentially, the detecting sensors 18, 1A-8A are secured to an electronic anchoring card 23, which in turn is secured to the support member 17 for the sensors.
In particular, as shown in
The anchoring card 23 for the sensors 18, 1A-8A also forms the operative connection between the sensors 18, 1A-8A and the electronic control unit 22, by means of at least one electrical connecting element 27, shown in
Preferentially, the detecting sensors 18, 1A-8A are of the optical type, as shown in
As an alternative, the detecting sensors 18, 1A-8A can for example be in the form of microswitches 28, as shown in
The electronic control unit 22 is operatively connected to an external connector 29 provided on the closing cover 21, by means of a disengageable terminal 30, thereby enabling the electrical connection of the detecting system 16 with a general unit (not shown) for the management and control of the different retaining devices 10 provided along the production lines.
The electronic control unit 22 is also provided with light emitting diodes (LED) 31 designed to provide luminous indications relating to specific functional conditions of the clamping device 10, which are visible on the outside through appropriate holes 32 provided in the closing cover 21.
However, a solution without the side opening 20 in the box-shaped body 11 of the device 10, and the respective closing cover 21 is not excluded, the detecting system 16 being in this case partially accessible from the outside through appropriate holes in the box-shaped body 11, in such a way as to be able to make an operative connection of the system 16 with the aforesaid general management and control unit, and to be able to set the control unit 22 of the sensors 18, 1A-8A by means of appropriate activating means, which will be described hereunder.
According to a first embodiment shown in
The self-learning microprocessor 33 in particular is programmed for selectively activating a sensor 1A-8A of the plurality of sensors 1A-8A, disposed in correspondence with a position which is acquired by means of repetition of a detection cycle, shown in
In particular, as shown in
In the event of a reading of the position of the retaining member 12 by the sensors 1A-8A not coinciding with the first reading carried out, the detection for self-learning re-start by repeating the first reading of the position of the retaining member 12 by the sensors 1A-8A, and then carrying out the steps described above until finding the correct position of the sensor 1A-8A capable of detecting the rest position of the retaining member 12.
In this way the selective activation of the sensor 1A-8A capable of detecting the rest position preset for the retaining member 12, takes place wholly automatically, without the need for any operation on the part of an operator.
Alternatively, as shown in
A further alternative is shown in
Contrary to what occurs for the control unit 22 shown in
In the light of the above, it can be said with all certainty that a detecting system according to this invention allows to detect different operative positions of the retaining member of any retaining device with the utmost precision, eliminating any need for operations by an operator aimed to modifying the physical configuration or positioning of the sensors of the detecting system, and at the same time ensuring the perfect functioning of the same devices.
In this way, whenever it is necessary to modify the functioning of the retaining devices, especially in the case of variation of the operative rest position, the time required for adjusting the same devices is drastically reduced, and consequently are reduced the machine downtimes of the production lines, necessary for enabling such operations, resulting in considerable economic advantages.
Moreover, the system for detecting operative positions according to the invention allows to make detections in different operative positions of the retaining member, corresponding to different conditions of use or control of the retaining device, by simply operating suitable switches for controlling the functioning of the detecting system, or by mere self-learning of an electronic control unit of the system, with advantages in terms of simplicity of operation by the operators, thereby limiting the possibilities of error.
The detecting system 16 for detecting operative positions can alternatively be used in other types of retaining devices 10, for example in a centering device for work pieces as illustrated in
In particular, in this case the centering device 10 comprises a retaining member 12, in the form of a centering rod, linearly movable between a forward operative position for retaining a work piece and a backward rest position for releasing the work piece, said member being operatively connected to drive means 13 by a longitudinally movable thrust element 14.
Moreover, the device 10 comprises a detecting system 16 for detecting the position of the retaining member 12 which has similar features to those already described for the previous case to which the reference is made.
What has been described and shown with reference to the accompanying drawings, has been given purely by way of example in order to illustrate the general features of the invention, as well as several of its preferential embodiments; therefore other modifications and variations to the detecting system for detecting operative positions in retaining devices for retaining work pieces are possible, without thereby deviating from the scope of the claims.
Number | Date | Country | Kind |
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MI2004001584 | Aug 2004 | IT | national |