WO1989007735A1

WO1989007735A1 - A method of producing thin plate structures such as reflectors for fluorescent lamp fittings

Info

Publication number: WO1989007735A1
Application number: PCT/DK1989/000037
Authority: WO
Inventors: Hans Møller THOMSEN
Original assignee: El-Selskabet Riegens A/S
Priority date: 1988-02-18
Filing date: 1989-02-17
Publication date: 1989-08-24
Also published as: DK82888A; DK161346B; DK161346C; AU3195989A; DK82888D0

Abstract

Fluorescent lamp reflectors consisting of two elongated side plates (2) and of a number of cross pieces (4) are normally made of a very thin, blank anodized aluminum plate material, the cross pieces being shaped and bent into a V-shape and fixed to the side plates by means of protruding lugs (30 and 32), which are stuck through slots in the side plates and bent out along the outer side of the plates. Traditionally this process is done manually, requiring great care. The invention provides a method by which the production may be effected in a rapid automatic manner, the cross pieces (4) being produced by an integrated operation and transferred to a holder gauge (24), whereafter side plates (2) leniently fetched from a storage (34) are moved so as to be mounted onto all of the lugs (30, 32) simultaneously, and thereafter all the lugs are bent out in one operation by means of a special lug folding tool (42). For receiving the lugs by moderate precision requirements, rather wide slots (26, 28) in the side plates are used, and the insertion of the side plates is carried out with the cross pieces (4) slightly compressed. The cross pieces are brought back to a correct cross sectional shape when the respective lugs (30, 32) are pressed out towards the ends of the slots (26, 28) in connection with the folding out of the lugs.

Description

A method for the production of thin-plate structures such as reflectors for fluorescent tube fittings.

The present invention relates to a method of pro¬ ducing products constructed by a pair of elongated side shells and a plurality of transverse members mounted therebetween, particularly reflectors for fluorescent tube fittings. Conventionally such reflectors are pro¬ duced by shaping said side shells with a desired arcuate cross-section from a strip material of thin-metal, e.g. 0.5 mm aluminum, whereas the transverse members are formed as substantially V-shaped elements likewise made of thin metal sheet with suitable arcuate sides. Hereby the transverse members serve both as shield elements and as elements for concentrating the light in downward direction, and it is also important that they form a firm connection between the side shells so that the complete reflector element can take the form of a self-contained, rigid unit which can be mounted in a fluorescent tube fitting.

Also the V-shaped transverse members are appro¬ priately produced of a corresponding thin sheet material, and beside the very production of the parts in question it is of essential importance how one can rationally handle the parts and bring about such a con¬ nection between them that a rigid self-contained struc¬ ture of the reflector element can be obtained.

In connection with said basic construction of these elements it is a natural measure that the side shells are prepared with holes for receiving end portions of the transverse members with the desired spacing of the transverse members, and that said members are correspondingly formed with projecting end portions or lugs which can be inserted in said holes and thereby attached to the side shells in a suitable manner. The relevant prior art technique of production teaches a substantially purely manual assembling of the parts and even about a quite troublesome forming of the V-shaped transverse members from punched blanks, in any case when it is desirable that the sides are made flat-parabolic, said shaping being carried out by pressing of the material against a shaping face by means of a manually operated pressure roller. True, the thin material is easy to bend, but the transverse members are to be produced in large quantities, and generally speaking it will be desirable to automatize at least this part of the process.

However, the purpose of the invention is to provide a method of fully automatic production of the objects referred to in their entirety. On the face of it one may wonder that this has not been implemented long ago; one reason may be the very fact that the manual handling enables individual adjustments to be made during the assembling in case of high tolerance requirements. The thin sheet components must be handled carefully, and during the many lug assemblings the lugs can relatively easily be brought in position opposite the receiving slots during successive mounting of the transverse members, which will be difficult to imitate mechanically. However, the demands on tolerance necessary to make the final result a mechanically stable structure can hardly be reduced.

Especially when said transverse members are pro¬ duced manually, tolerance deviations will inevitably occur which precisely in case of a high degree of re¬ quired accuracy can be rather easily compensated for by manual effort of a trained operator.

Thus a possible automation could be based on an automatic sensing of the tolerance deviations and a corresponding control of the parts in question, but such an imitation of the manual method would be very com- plicated.

Instead the invention goes the way of basing the production on a high degree of accuracy in the shaping and positioning of the elements to be assembled, so that the assembling can be carried out without the need of any kind of correction. This consideration goes to such great lengths as to imply an automatic production of the transverse members by which said members are exactly alike, as it must be ensured that these parts can be positioned exactly relative to the longitudinal plate members, to which they are to be connected. In order to avoid the manual work, the production of the transverse members should take place synchronized or coordinated with the supply of the longitudinal plate members.

Thus it is a basic aspect of the invention that the transverse sheet profile members are shaped by an auto¬ matic punching and shaping process and in^' immediate continuation thereof are transferred successively to a setting device in which the transverse members are arranged in a transverse line in accurate mutual positions, after which opposite elongate plate portions provided with premade slots for receiving lugs or lock lugs projecting from the ends of the transverse members, are brought to said line and thereupon carried against the ends of the transverse members while receiving said lugs in said receiving slots, after which the lugs are bent outwards by means of automatically working bending tools which are operating with suitable care.

The transverse members are relatively small and rigid units which can be reasonably easily handled with care, as they only need to be arranged accurately spaced in a line, after which they can be brought into engagement with the elongate plate portions in an almost passive manner, when said plate portions are pushed against the ends of the transverse members. However, it is an essential feature of the invention that the lugs can be received in quite broad slots, even with the transverse members in a slightly squeezed condition, whereby a subsequent accurate engagement between the lugs and the respective ends of each slot can be obtained without particularly heavy demands on tolerance during the insertion of the lugs. It is of particular importance to handle the elongate sheet portions in a requisite careful manner, as said portions - especially in connection with reflectors - are easily deformed in a noticeable manner by even the least local overload or differential load.

In the present invention it is preferred that the elongate side plate members are preshaped, although preferably in an integral machine section, with the desired profile and the desired length from a rolled up sheet strip material material, and that said plate members which are also formed with the requisite receiving slots for the lugs of the transverse members are automatically or manually transferred to be packed in a pair of magazines for respective side plates of the reflector structure, and further that means are used for successive picking up of said plate members from said pair of magazines and positioning of the plate members opposite the line of transverse members with the required accuracy as well as to subsequently carry the plate members against the ends of the transverse members. During the development of the invention several different transfer devices have been made and tested, and one of them has proved much preferable, viz. a device for gripping, transferring and pushing in of the plate members by means of a series of suction cups, which may either hold the plate in firm engagement with a moved carrier or in connection with a relatively close mutual positioning may be well suited both for holding the blanks during a movement away from the magazines and for acting as suitably yielding pressure elements during the subsequent pushing in of the blanks against the ends of the transverse members.

As to the bending out of the lugs on the ends of the transverse members it should be remarked only that this bending most appropriately takes place by means of tool parts which are moved to perform direct lateral bending of the lugs rather than by tools causing a bending out merely by being pressed axially against the lugs for bending out said lugs by an associated trans¬ verse force component. However, the last portion of the lug bending may appropriately be performed by a direct inwardly directed pressure.

In the following the invention will be explained in more detail with reference to the drawing in which

Fig. 1 is a schematic perspective view illustrating the basic assembling of the parts in a method of the invention,

Fig. 2 shows in elevation a detail of Fig. 1, Fig. 3 is a partial view of an assembly under pro¬ duction,

Figs. 4 and 5 are views serving to illustrate a lug bending operation,

Fig. 6 is a perspective view of various tools, Figs. 7 and 8 are end and side views of the resulting product, and

Fig. 9 is a perspective view thereof. For the production of a fluorescent tube reflector as shown in Fig. 9 consisting of a pair of opposite elongate side plates 2 and transverse members 4 located therebetween, said components are produced separately, and at the bottom of Fig. 1 a preferred method of pro¬ ducing the transverse members 4 is illustrated. These members are made from a sheet strip 6, which is carried from a supply roll not shown to a punching device 8 in which blanks 10 are currently punched for forming the transverse members. These blanks are carried by non- illustrated conveying means to a stamping device 12 provided with gull wing shaped press faces as shown, which deform the blanks 10 correspondingly, the upper part of said tool being made of hard material with very accurately shaped moulding faces, whereas the lower part is made of semi-soft material. Thereupon the moulding pressed blanks are placed on the top of a forming block 14 provided with a substantially V-shaped central de¬ pression 16, into which the blanks are pressed by means of a press tool 18 for bending the transverse members into the desired final shape. Here, too, the lower part 14 consists of semi-soft material, whereby the outer side of the blanks are taken care of during the involved sliding of the outer side along the upper edge areas of the depression 16. The block 14 must not necessarily be provided with the depression 16, as the desired bending of the blank may be carried out by pressing down of the tool 18 against a flat surface of the semi-soft block, whereby the bending results from a quite brief pressing down. By this the outer side faces are guarded against scraping. Already in the punching device 8 or preferably in the stamping device 12 the opposite edge portions along the short sides are bent into angle flanges 20, which in the finished transverse members 4 are inwardly projecting in a common, upper horizontal plane. However, these angle flanges are not indispensable.

The transverse members thus finished are carried successively from the forming block 14 to a V-shaped receiving recess 22 in a transverse jig bar or chain 24, which is moved stepwise to the^' left, so that a long length of the bar or chain is filled step by step with transverse members in the recess 22, i.e. over a length corresponding at least to the length of the side plates 2 to be used. As shown in Fig. 2 the transverse members 4 are inserted in the recess 22 to assume a hanging position therein so that room is left for the transverse members to be pressed slightly down in order to obtain a completely stabilized reception in the recess.

The side plates 2 having slightly arcuate cross section are produced by stamp deforming or rolling of band material, which may very well take place in the same machine assembly as that in which the transverse members 4 are produced, without, however, being restricted thereto. The side plates are provided with punched slots 26 and 28 for receiving projecting lugs 30 and 32 respectively at the top and bottom of the side edges of the transverse members 4. No matter how or where the side plates are produced they are placed in two magazines 34 on their respective sides of the bar or chain 24 (only one magazine is shown) , where the side plates 2 are placed in a stack suspended on carrying pins 35 and/or supported by carrying and supporting faces in such a manner that the side plates are rather accurately positioned with relation to the machine frame, in which the transverse bar or chain 24 is mounted, which applies both vertically and longitudinally, but not necessarily in the stacking direction. The carrying pins cooperate with holes 37 in the plates 2, which holes are intended for use in the subsequent mounting of the reflector in a fluorescent tube fitting.

For transferring the respective front side plates 2 of each of said stacks to a position by the side of the bar or chain 24 a beam 36 is used which is provided with a number of projecting pipe stubs 38, the outer ends of which are provided with a suction cup 40. The beam 36 is connected to a moving mechanism not shown, by means of which the beam can be moved inwards towards the front side of the stack in a direction of movement exactly identical with the stacking direction, so that the suction cups 40 can grip the front side plate 2 of the stack with an accurate mutual positioning irrespective of the thickness of the stack when the gripping takes place. The moving mechanism is arranged to thereafter carry the beam 36 into a correspondingly accurate position opposite the side of the bar or chain 24, so that the slots 26,28 in the side plate 2 will be located in alignment vith the projecting lugs 30,32 of the transverse members 4 embedded in the bar or chain 24.

The slots 26 and 28 in the plates 2 are not narrow slots for local reception of the respective lugs 30 and 32, but wide slots being able to receive at the opposite ends both lugs 30 and both lugs 32, respectively, with a view for enabling the opposite lugs to be bent away from each other over the opposite end edges of the slots.

For safe guidance of the movement of the plates 2 against the side edges of the transverse members 4 it is important that said movement can take place without the lugs 30,32 colliding with the plate 2 outside the slots 26 and 28, whereas it is also desirable that the lugs be in close engagement with the end edges of the slots. In the invention this problem of tolerance has been solved in that prior to the final movement of the plate members 2, the transverse members are pressed down in the recesses 22 by means of an overhead press beam not shown, whereby (cf. Fig. 2) the V-shaped transverse members will be pressed resiliently together at the top to thereby reduce the spacing of the opposite lugs 30 and 32 of the respective pairs of lugs. As shown in Fig. 3 the lugs may in this way be introduced fairly freely into the slots 26,28, although especially at the bottom little space is available. In return the transverse members 4 are here held exactly by "the pressing down against the bottom of the V-recesses 22 in the bar/chain 24, so that the blanks are securely positioned.

After this bringing in of the side plates 2 over the lugs 30,32 provision is made for lowering the bar/ chain slightly or alternatively for raising the beams 36 with the intermediate, provisionally assembled object slightly, so that the transverse members 4 are raised from the recesses 22 and thus are allowed to expand with the result that the lugs 30 and 32 move outwards towards or against the respective end faces of the slots 26,28. Of course, also the said overhead press beam must be raised, or corresponding relative movements may be established in other ways.

Thereupon a working tool 42 is brought in position opposite the respective pairs of lugs as shown in Figs. 4 and 5. The front face 44 of the tool is arcuate corre¬ sponding entirely or fairly to the cross-section of the side plate 2; a pair of projecting tapered bending noses 46 and 48 positioned one above the other extends from said front face for cooperation with the pairs of lugs 30 and and 32, respectively. The tool is carried into the position A shown in Fig. 5, after which it is moved laterally, first outwards past one lug 30 to partly bend this lug outwards by the passage of the bending nose 46 and next back and further outwards in the opposite direction to correspondingly bend the other lug 30. Thus, as shown both lugs will be bent obliquely outwards about the end edges of the associated slot 26, when the bending nose has reached the shown position B. Sub¬ sequently the tool is carried back to position A, after which it is activated to move inwardly against the side plate 2. Thereby the front face 44 presses the obliquely bent lugs against the plate 2, i.e. to complete bending out of the lugs.

The object will now be finished, i.e. it only has to be released from the holding tools in a suitable manner.

It appears from Figs. 6 and 7 that normally there will be room both for a tool beam 50 carrying the tools 42 and for the beam 36 as here having holding heads 35 with suction cups 40 at an outer face of engagement for the side plates 2. Lowermost the head 35 is provided with a pointed, short projecting pin 52, which on the activation is introduced into one of the previously mentioned holes 37 in the plate 2 to thereby secure said plate against movements in its own plane. Hereby an accurate positioning of the plates as well as an effective holding thereof during the lug bending by the tools 42 are obtained.

Only a few holding heads 35 spaced throughout the length of the supporting beam 36 are needed. There may furthermore be provided some longer downwardly extending supporting blocks 33, which may possibly be integral with the holding heads outside the working area of the bending tools 42.

At the ends of the reflector it may be desirable to terminate with the relevant inwardly facing half part of a transverse member 4. Such a half part is shown by 4' in Fig. 9, mounted at the right end of a series of transverse members, which are prepared to receive the side plates 2. The blank has been made by punch cutting of an ordinary blank 10,4 so that the half transverse member has an outwardly bent edge portion 54 at its bottom, Fig. 8. The ends of the side plates 2 are pro¬ vided with one half of the ordinary slots 26 and 28, notches 56 spaced some distance from the edge being cut in the longitudinal edges of the slots so that flap portions 58 of the plate material are left outside said notches. The half transverse members can be laid up and positioned quite like the other transverse members, leaving only the problem that the counter action other¬ wise provided by the opposite half of the transverse member is missing, which means that the mounted half part will not be stabilized against outgoing release from its engagement with the plates 2. This, however, is remedied by the flap portions 58 which can be pressed inwards to form a blocking on the outer side of the transverse member 4 ' .

This inward pressing is performed automatically by the previously mentioned pressing in of the lug bending tools 42, the bending noses 46 and 48 of which (Figs. 4 and 6) being provided with vertically thickened base portions 49 which by said pressing in will just engage with the flap portions 58 to bend them into blocking positions outside the element 4'.

Thus, application of tools 42 with said base portions 49 is needed only at the two ends of the reflector; however, it has been found expedient to standardize the tools in that respect, i.e. because this gives wider latitude for the production of reflectors of different lengths and in different mounting positions with relation to the bar or chain 24. In return this means that the base portions 49 throughout the length will attempt to depress the plate material on each working place, and this would be flatly undesirable. For this reason all of the slots 26 and 28 except the outer¬ most are shaped with adjoining openings 29 which receive the base portions 49 during the pressing in of the tools 42.

It is of great importance that the transverse members 4 are so assembled with the plate members 2 that the edges are in full and accurate contact with the plates both for the sake of the structure and in order to ensure that no visible "black stripes" are formed internally of the reflector; the surfaces of the reflector being bright, a slit between not closely fitting parts will appear visually as a black stroke which is undesirable. By the invention quite tight assemblies can be made automatically and very rapidly, as also the parts are handled in such a manner that the surfaces are spared rubbing which could harm the bright¬ ness.

Of course, in using the termination shown in Fig. 8, care must be taken that the blanks 4 are subjected to the requisite modification by an additional tool section, as the punching of the slots in the plate members 2 must be adjusted by lacking removal of the flap areas 56. All this causes no difficulties in principle, and the associated means can easily form part of an automatic control system, which can direct the various operations on the basis of keyed order data with respect to number and length of the desired blanks. It will even be possible to switch automatically between different lines of tools for production of the plate members 2 and the transverse members 4 respectively as also between different holding bars or chains 24 and different sets of supporting beams 36 and lug bending beams 50, so that switching between different types or sizes of blanks is feasible.

As the operations are to be executed with a rather high degree of accuracy, it may be appropriate to perform transfer movements in several stages, e.g. by taking the side plates from the magazine 34 by means of a conveying beam 36, which is utilized only to transfer the plates to temporary deposition in an intermediate station close to the final mounting place, whereupon a special gripping beam, cf. Fig. 6, grips the plates in this station and carries them the short distance to the mounting place. In the intermediate station a very accurate adjustment of the position of the plates can be made, so that required exactness is secured, when the movement of the gripping beam is controlled precisely, whereas a correspondingly great accuracy in the pre¬ ceding handling of the plates may be dispensed with. Likewise, the transverse members may be laid up in an only fairly accurately made holding bar or chain 24, from which they may then in a suitable manner be trans¬ ferred to a more accurately made holding device for execution of the mounting itself. The demands on accuracy must just be seen in the light of the fact that movement through several links is involved, whereby a fundamental sufficient tolerance must be able to accommodate several accumulated inaccuracies, i.e. these should be quite small.

Claims

C L A I M S :

1. A method of producing thin-plate elements such as reflectors for fluorescent tube fittings, consisting of a pair of elongate side plates and a number of transverse members mounted therebetween and having the form of V-bent plate members with projecting lugs at the ends, which lugs are introduced into slots in the side plates and bent for assembling of the parts, characterized in that the transverse members are made successively by punching, pressing and bending and supplied to an elongated holding jig in which they are placed in a series in mutual positions corresponding to their mutual final positions, and that the side plates are seized from a magazine and carried to a position opposite the ends of the transverse members by means of a holding beam which holds the side plates by suction in engagement with correspondingly profiled supporting face portions on the holding beam, after which the side plate on the holding beam is pushed against the ends of all of the transverse members at the same time as another side plate is correspondingly pushed against the opposite ends of the transverse members, said transverse members being kept slightly resiliently squeezed together for temporary reduction of the spacing of their oppositely positioned end lugs, which lugs during said pushing are carried through wider slots in the plates and after the introduction are affected in outward direction against the end edges of said slots during expansion of the slightly squeezed transverse members and subsequently further in the same direction for bending out the respective lugs about the said edges of the slots.

2. A method according to claim 1, characterized in that during the pushing of the side plates and the subsequent bending effect on the lugs, said side plates are held centered on the holding beam by means of pins projecting therefrom and extending through closely fitting holes in the side plates.

3. A method according to claim 1, characterized in that the bending of the lugs is performed by means of reciprocating tools having projecting nose portions which from a position between the opposite lugs are carried first in one direction to partly fold out one lug and next in the opposite direction to partly fold out the opposite lug, whereupon the nose portion is returned to the initial position between the lugs, and the tool is pushed against the side plate to fold out and press the lugs against said plate with the nose portion extending through the free space in the plate slot between the lugs.

4. A method according to claim 1, characterized in that the transverse members are produced successively from a supplied sheet band material in a working station from which the finished members are immediately transferred to said holding jig or another receiving or transfer unit, which is moved past a delivery end of the working station for successive receipt of the members at intervals.

5. A method according to claim 1, characterized in that prior to the pushing on of the side plates, the transverse members are slightly squeezed by being pressed down into the V-shaped holding recesses in the holding jig by means of a throughgoing overhead press beam.

6. A method according to claim 1, characterized in that the transverse members are subjected to a mould pressing by means of a matrix die against a backing block of semi-soft material.

7. A method according to claim 1, characterized in that the side plates at the ends are connected to respective half-parts of said transverse members, flap portions of the side plates just outside the transverse members being bent in to secure said half-parts against outgoing movement.