GB2035942A - Positioning apparatus for a workpiece carrier - Google Patents

Abstract

Apparatus, for positioning a workpiece carrier (11) at a work station (10) of a production line conveyor (12, 12), includes a lifting device (18, 17, 33) which can operate in two stages. In the first stage the lifting device lifts the carrier from the conveyor (12, 12) and positions it without undue precision at the work station. In the second stage the lifting device lifts the carrier further, such that it is precisely positioned by pins (45, 46) entering recesses (48, 49) at the work station. <IMAGE>

Description

SPECIFICATION Positioning apparatus for a workpiece car rier The invention relates to positioning apparatus for bringing into position workpiece carriers supplied on a conveyor along a transportation path to a work station in a production line, particularly to an assembly machine, with a stroke producing device by means of which the workpiece carrier can be moved in a locating-stroke movement transverse to the transportation path of the conveyor in order to cause fitting means provided on the work piece carrier to engage with fitting means constructed complementary thereto, and to locate the workpiece carrier relative to a fixed point.

Apparatus of this kind is known from DD-PS 122 336 in which the fitting means serve simultaneously during location for exact alignment. This calls for costly manufacture of the locating means, which is required even when exact alignment may not be necessary in some work stations.

A further disadvantage of the known positioning device consists in the fact that the expensive aligning elements and aligning bores which form the locating means become worn relatively rapidly and must then be re placed.

The invention is based on the problem of creating positioning apparatus of the kind described which makes possible a simplified and less expensive method of construction for the work stations when work stations are involved where an extremely exact position alignment is not required during location of the workpiece carrier.

According to the invention this problem is solved in positioning apparatus of the kind described in the introduction by dividing the locating-stroke movement of the stroke pro ducing device into two stroke stages, the first of which is provided for positioning and the second for locating the workpiece carrier, and by providing on the stroke producing device, for the positioning, at least one fitting device which co-acts with the associated complementary fitting device on the workpiece carrier during the first stroke stage.By means of the fitting devices which are effective between the stroke producing device and the workpiece carrier, a first positioning is achieved in the first stroke stage; a preliminary positioning with a relatively large tolerance range is con cerned here, since the movable stroke produc ing device is not suitable for aligning with a high level of accuracy. There is now a choice between the possibility during the second stroke stage, thus during the locating process, of bringing high-precision alignment means on the workpiece carrier and a fixed point on the work station into engagement with each other, or being content with the preliminary positioning already carried out and fixing the workpiece carrier at the work station with the alignment produced by the preliminary positioning.The latter possibility, which results in a simplified and cheaper construction of the work station, exists whenever the work station is one in which simpler assembly or machining processes are carried out and where precise alignment of the workpiece carrier is not involved.

However, if precise alignment is required in a certain work station, the invention affords the additional advantage of reducing operating costs in that the bringing together of the accurately produced alignment elements and alignment bores in the second stroke stage is effected very gently and therefore with little wear, since due to the preliminary positioning which has already been carried out during the preceding first stroke stage, the workpiece carrier has been set up in a position in which the bringing together of the exact fitting means used for the precise alignment can be carried out without any difficulty, thus achieving an extension of the working life of the expensive fitting means.

The invention is explained in detail in the following with reference to the Drawing.

Figure 1 is a partially cut-away and sectioned, schematically simplified front view of an embodiment example of a work station with a workpiece carrier brought into it.

Figure 2 is a schematically simplified plan view onto the workpiece carrier.

Figure 3 is a schematically simplified plan view onto the work station shown in Fig. 1, without the workpiece carrier.

Figure 4 is a schematic scrap view, showing a partially sectioned detail from Fig. 1 drawn on a larger scale, in which various working positions of the workpiece carrier relative to the work station are indicated.

Fig. 1 shows an embodiment example of a work station designated 10 as a whole, with a workpiece carrier 11 located therein. As can be seen best in Fig. 2, the workpiece carrier 11 is substantially in the shape of a square plate, on the upper face of which clamping or fixing means (not shown) are arranged for clamping or accommodating a workpiece (also not shown), and which is moved, with its lower face resting on a friction-roller conveyor 12, along a desired transportation path up to and through the appropriate work stations. In the example shown the roller conveyor has friction-locked driven rollers 13. As can be seen in Fig. 1, the roller conveyor 12 runs through the work station over a frame 15 belonging to the latter. Strips 14 are fitted on either side of the roller conveyor to prevent the workpiece carriers 11 from sliding laterally off the roller conveyor 1 2.

In Fig. 1 the workpiece carrier 11 is lying in its transportation position, which is also drawn in in Fig. 4 in full lines, directly on the rollers 13 of the roller conveyor. The friction drive of the rollers 13, which is not shown, operates continuously, so that an advancing force in the transportation direction acts continuously on the workpiece carrier 11 lying on the conveyor 12. In order to bring the workpiece carrier to a standstill in the work station a stop 16 is provided which is connected to a bearing plate 17 which can be raised by means of a lifting device designated 18 as a whole, in order to move the stop 16 into the movement path of the transportation movement of the workpiece carrier 11 and to bring the latter to a standstill without stopping the friction roller conveyor 12.In the embodiment example shown, the lifting device has three lifting cylinders 19, 20 and 21 which, as will be explained in more detail again later, can be actuated independently of each other in order to lift the bearing plate 17 in such a way that its vertical movement is effected in stages.

When the lifting cylinder 19 is actuated the bearing plate 17 and with it the stop 16 is lifted sufficiently far for a workpiece carrier 11 running into the work station to run up against the stop 16 via its abutment surface 22. For its vertical movement the bearing plate 17 is connected to columns 23 which can be displaced in a column guide designated 24 as a whole, which is attached to the frame 15.

The working stroke of the lifting cylinder 19 is transmitted via its piston rod 25 to the piston rod 26 of the lifting cylinder 20 disposed above, whereby this is raised up together with the lifting cylinder 21, which is attached to it and which lifts the bearing plate 17 via its piston rod 27.

In order to be able to carry out work on the workpiece in the workpiece carrier 11 brought to a standstill in the work station 10 by means of the stop 16, such as an assembly sequence or a machining process, the workpiece carrier 11 must be clamped in a fixed position in the work station. This clamping is effected by lifting up the workpiece carrier from the roller conveyor 12 and moving it sufficiently far vertically upwards for it to become clamped firmly by pressing contact surfaces 29 which are constructed in the corner zones of the workpiece carrier against locationally fixed contact surfaces 30 on the work station. The contact surfaces 30 on the work station are formed by the lower faces of clamping strips 31 which are attached to uprights 32 which are attached in turn to the frame 15 of the work station.

The locating-lifting movement for clamping in the workpiece carrier 11 in the work station 10 is accomplished by a lifting plate 33 which is connected via an intermediate part 34 to the bearing plate 17. Underneath the intermediate part 34 the piston rod 27 is attached to the bearing plate 17. Attached to the upper face of the lifting plate 33 there is a plate 35 extending radially over the edge of the plate towards the outside (see in particular Fig. 3), two positioning pins 36 and 37, and two supporting discs 38 and 39. On its radially outside end the plate 35 is bent upwards perpendicularly to form the stop 16 which has already been mentioned.The positioning pins 36 and 37 each have a collar 40 or 41 respectively in their lower region, the height of which collars, measured from the upper face of the liftiing plate 33, corresponds to the height of the plate 35 and the supporting discs 38 and 39. The upper faces of the collars 40, 41, the plate 35 and the supporting discs 38 and 39 form the supporting surfaces which rest against the lower face of the workpiece carrier 11, in order to raise the latter during the locating-lifting movement to clamp it in the work station. During this process the positioning pins 36 and 37 enter into associated locating bores 42 and 43 respectively (see Fig. 2) in the workpiece carrier 11.

The locating-lifting movement of the workpiece carrier 11 which has been halted by the stop 16 is effected in two lifting stages, the first lifting stage serving for the preliminary positioning of the workpiece carrier 11 before it is clamped in the work station. For this lifting stage the lifting cylinder 20 is actuated, in order to raise the lifting plate 33 sufficiently far for the positioning pins 36 and 37 used for the process of preliminary positioning to enter into the locating bores 42 and 43; and then for the workpiece carrier 11 to be lifted off the roller conveyor 12 by application of the supporting surfaces of the lifting plate 33, and moved upwards from the transportation position drawn in Fig. 4 in full lines into an intermediate position indicated with dashed lines, in which the contact surfaces 29 are still a considerable distance from the locationally fixed contact surfaces 30. If, after the preliminary positioning, the second lifting stage is then effected by further actuation of the lifting cylinder 21, the workpiece carrier 11 is raised up out of this intermediate position sufficiently far for the contact surfaces 29 and 30 to b#e pressed against each other, and the workpiece carrier 11 is thereby clamped in the work station 10. This second lifting stage of the locating-lifting movement of the workpiece carrier 11 is indicated in Fig. 4, also with dashed lines.

The diameter of the pins 36 and 37 which are used for the preliminary positioning is somewhat less than that of the associated locating bores 42 and 43. This means that during the preliminary positioning the workpiece carrier 11 is still not lined up in a very exactly defined position, but at first there is only alignment within a relatively wide tolerance range. Due to the comparatively small diameter of the pins 37 and 38 relative to their associated bores, the advantage is obtained that reliable insertion of the pins in the bores is ensured, although the workpiece car rier is supplied by the roller conveyor 12 with relatively uncontrolled alighment and only a simple and inexpensive stop 16 is used to bring the workpiece carrier to a halt.When the work which is to be carried out in the work station involved does not call for very exact positioning of the workpiece and therefore of the workpiece carrier, the latter can be clamped without more ado during the second lifting stage against the contact surfaces 30 with the positional alignment in which it is found after the preliminary positioning. How ever, if very exact lining-up of the workpiece carrier 11 in the work station 10 is required, during the second lifting stage, before clamp ing, a precise positioning is carried out. For this purpose, fine-positioning pins 45 and 46 disposed in two diametrically opposite corner zones of the workpiece carrier 11 extend upwards within the range of the contact surfaces 29.These fine-positioning pins are designed to engage in fine-positioning bores 48 and 49 which are formed in sleeves 50 which can be inserted in recesses in the clamping ,strips 31.

During the second lifting stage of the work piece carrier 11 the insertion of the fine positioning pins 45, 46 in the fine-positioning bores 48 and 49 is effected with a high level of operational reliability, since the workpiece carrier 11 has already assumed a fairly exactly defined position due to the preceding prelimi nary positioning, and the pins can find their way into the bores without any special mea sures being required.

If, as already mentioned, fine-positioning of the workpiece carrier 11 is not required in a certain work station, so that the workpiece carrier 11 can be simply clamped in at the work station in the position it has assumed after the preliminary positioning, the sleeves 50 in the clamping strips 31 can be omitted, so that the fine-positioning pins 45, 46 extend into the recesses free of the sleeves 50 without fine-positioning during the second lift ing stage, when the workpiece carrier 11 is clamped in. The omission of the exactly-machined sleeves 50 affords a substantial reduction in the production costs of the work station concerned. If the accuracy of the alignment by the preliminary locating of the workpiece carrier is adequate for the work to be carried out in all the work stations in a production line, the positioning pins 48 and 49 may also be omitted.

Since there are four clamping strips 31 at the work station in the embodiment example, all the clamping strips 31 may be equipped with sleeves 50 with fine-positioning bores, if required, so that in addition to the fine-positioning bores 48 and 49 there may also be two further fine-positioning bores 58, 59 as indicated with dashed lines in Fig. 3.

The division of the locating-lifting movement into two lifting stages opens up the particularly advantageous possibility of rotating the workpiece carrier 11 which has been brought to a halt in the work station, in the work station itself. Special rotating stations arranged in front of and after the work stations are thereby made superfluous.The workpiece carriers 11 can be transported on the roller conveyors 12 between the work stations 10 irrespective of which. rotary position is required for the work to be carried out in the work station concerned, thus always with a constant specific transportation alignment, so that the workpiece carriers do not have to be equipped with buffers 52 on all four sides, but only on the side which is at the front in the transportation alignment, and on the opposite, rear side, The same applies to the abutment surfaces 22 which, although two abutment surfaces 22 are shown in the Drawing, only need to be pressent on the workpiece carrier 11 on its front face in the transportation direction.

The lifting plate 33 acts as part of the rotating device for rotating the workpiece carrier 11, which in the embodiment example is intended for rotary angles of up to approximately 100 . If larger angles are involved other types of known rotary devices, such as rack drives, are brought into use. In the embodiment example the intermediate part 34 which is pemanently connected to the lifting plate 33 is rotatably mounted on the bearing plate 17. A pivot arm 53 extending radially from the intermediate part 34 is connected to a piston rod 54 of a pivoting cylinder 55 mounted pivotably at 55' on a projection 17' on the bearing plate 17.After preliminary positioning has been completed, when the workpiece carrier 11 is raised up off the roller conveyor 12 and lifted into an intermediate position, in which there has still not been any positioning (see Fig. 4), a rotary movement of the lifting plate 33 induced by actuation of the pivoting cylinder 55 is transmitted to the workpiece carrier 11, with the positioning pins 36, 37 provided for the preliminary positioning acting as entrainment means.

If a rotary angle which differs from 90 or 1 80' is involved in a work station with a rotating device, in this work station instead of four clamping strips 31 against which the contact surfaces 29 of the workpiece carrier 11 are clamped, only two other clamping strips can be provided, since with such rotary angles as a rule two diametrically opposite corner zones of the workpiece carrier 11 are located inside the area of the transportation path, which must remain free from pieces of apparatus.In such a case it is sometimes necessary to provide not only two diametrically opposed fine-positioning pins 45, 46, but also, for co-action with the clamping strips arranged correspondingly in the work station concerned, a further pair of fine-positioning pins 56 and 57 arranged diametrically opposite in the other two corner zones inside the contact surfaces 29, this being, as indicated in Fig. 2 in dashed lines, preferably in an arrangement symmetrical with the rotary axis of the rotary movement of the workpiece carrier 11, as is also preferably the case with the other fine-positioning pins.

In the embodiment shown in the Drawing the clamping strips 31 with the fine-positioning bores are arranged in such a way that rotating and clamping of the workpiece carrier 11 is only possible with a rotary movement through 90 or 180'.

Claims (8)

1. Positioning apparatus for bringing into position workpiece carriers supplied on a conveyor along a transportation path to a work station in a production line, particularly to an assembly machine, with a stroke producing device by means of which the workpiece carrier can be moved in a locating-stroke movement transverse to the transportation path of the conveyor, in order to cause fitting means provided on the workpiece carrier to engage with fitting means constructed complementary thereto, and to locate the workpiece carrier relative to a fixed point, characterised in that the locating-stroke movement of the stroke producing device (18, 33) is divided into two stroke stages, the first stage of which is provided for positioning and the second stage for locating the workpiece carrier (11), and that, for the positioning, at least one fitting device (37) is provided on the stroke producing device (1 8, 33), and co-acts during the first stroke stage with the associated complementary fitting device (43) on the workpiece carrier (11).

2. Positioning apparatus according to Claim 1, characterised by a rotating device (53 to 55) for rotating the workpiece carrier (11), which has been moved from the conveyor during the first stroke stage, through a predetermined rotary angle.

3. Positioning apparatus according to Claim 1 or 2, characterised in that, for the fine-positioning of the workpiece carrier (11) which follows during the second stroke stage of the locating-stroke movement, on the workpiece carrier and on the work station (10) second fitting means (45, 46, 48, 49) are provided, constructed complementary to each other, the dimensions of these being chosen so that the fine-positioning is effected with relatively close tolerances compared with the preliminary positioning carried out during the first stroke stage.

4. Positioning apparatus according to Claim 3, characterised in that, with a substantially rectangular workpiece carrier (11), a fine-locating pin (45, 46) is arranged at least in the vicinity of each of two diametrically opposite corners thereof, as the fitting means for the fine-positioning.

5. Positioning apparatus according to Claims 2 and 4, characterised in that a finepositioning pin (45, 46, 56, 57) is disposed in the vicinity of all four corners of the workpiece carrier (11).

6. Positioning apparatus according to Claim 5, characterised in that, as fitting means for the preliminary positioning, on the stroke producing device (1 8, 33) and on the workpiece carrier (11) there are at least two preliminary locating pins (36, 37) which become engaged during the first stroke stage of the locating-stroke movement, that at least that part (33) of the stroke producing device (1 8, 33) which co-acts with the workpiece carrier (11) can be rotated by means of the rotating device (53 to 55), and that the fitting means (36, 37, 42, 43) provided for the preliminary positioning also serve as entrainment means for rotating the workpiece carrier (11) during the rotary movement.

7. Apparatus for positioning a workpiece carrier at a work station of a transport path for workpieces, the apparatus including a stroke producing device operable in either one or two stages to move the carrier from the path at the work station, the arrangement being such that in the first stage the stroke-producing device moves the carrier and positions it without undue precision, and in the second stage, moves the carrier further to bring into operation locating means which position the carrier precisely at the work station.

8. Apparatus for positioning a workpiece carrier at a work station of a transport path for workpieces, the apparatus being constructed and arranged substantially as herein described and shown in the drawings.