DE8629956U1 - Folding arm for the projection head of work projectors - Google Patents

Description

Folding arm for the projection head of work projectors

The invention relates to a folding arm for the projection head of work projectors. Folding arms are already known, particularly for work projectors that work according to the incident light principle, i.e. where the projection lamp and lens are arranged in the projection head. These are portable work projectors whose dimensions can be reduced by folding away the projection head so that they can be transported easily in a handy carrying bag. However, the known solutions have the disadvantage that locks on the folding arm have to be released and that the parts of the arm and the projector head have to be swiveled in certain directions with both hands. In addition, the underside of the projection head points upwards in the rest position. If the work projector is not covered, the optical parts of the projection head can collect dust.

The invention is based on the object of avoiding these disadvantages and of creating a folding arm that can be operated very easily with just one hand.

This object is achieved according to the invention in that the folding arm is designed as a double parallelogram arm, the lower parallelogram half of which is hinged to the work surface and the upper parallelogram half to the projection head and that both parallelogram halves are hinged to one another via a common coupling piece, and that a catch is provided for both parallelogram halves, which holds the folding arm in its extended end position

in which the projection head is in its operating position. The further development of the invention can be found in the subclaims.

The advantages that can be achieved with the invention are in particular that the folding arm can be operated with one hand, whereby the actuation forces are very low due to the spring support. When folding, the lens head is not swiveled. The sensitive optical parts are thus protected by the working surface of the projector when folded. The closed top of the lens head prevents dust from entering. Since the lens head always moves in the optical axis when folded, it is possible, if desired, to provide additional locking mechanisms, e.g. for DIN A 5 projection.

An embodiment of the invention is shown in the drawing and is described in more detail below.

Show it

Figure 1 shows a working projector with the lens head in the projection position, in side view.

Figure 2 shows a working projector in the folded state in side view.

In the drawing, 1 denotes a folding arm of a work projector 2. The folding arm 1 is designed as a double parallelogram arm, the lower parallelogram half 3 of which is formed by two arms 4 and 5 and the upper parallelogram half 6 of which is formed by two arms 7 and 8. The two arms 5 and 6 of the lower parallelogram half 3 can be pivoted by means of bolts 9 and 10 on a

of the working projector 2. The upper ends of the arms 4 and 5 are guided to a coupling piece 13 and are articulated there by means of bolts 14 and 15. The arms 7 and 8 of the upper parallelogram halves 6 are also articulated to the coupling piece 13 by means of bolts 16 and 17. The arms 7 and 8 are guided with their upper ends to a connecting piece 18 of a projection head 19. The arms and 8 are articulated to the connecting piece 18 by means of bolts 20 and 21.

Feet 22 are attached to the underside of the worktop 11. A mirrored Fresnel lens 21 is arranged on the top of the worktop 11.

The connecting piece 18 of the projection head 19 is provided with a handle 24. A lighting device 25, a lens 26 and a deflecting mirror 27 are arranged in the projection head 19. The deflecting mirror 27 can be folded about a pivot point 28 into the position shown in dashed lines in the drawing.

The arms 4 and 7 of the parallelogram halves 3 and 6 have teeth 29 and 30 that mesh with one another. A catch 33 rests on flats 31 and 32 of the two arms 4 and 7. The catch 33 is pushed against the flats 31 and 32 by the force of a spring in the position of the arms 4 and 5 shown in Figure 1 and locks the double parallelogram arm in this position. A handle 35 is arranged on the coupling piece 13.

A compression spring 37 is attached to a pin 36 on the arm 4, which is guided on the bolt 10 of the arm 5. A compression spring 39 is attached to a pin 38 arranged on the arm 7, which is guided on the bolt 21 of the arm 8.

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In Figure 1 of the drawing, the projection head 19

of the work projector 2 is held in its projection position by the extended folding arm 1. The light thrown in a bundle by the lighting device 25 of the projection head 19 onto the worktop 11 is reflected by the mirrored Freenell line 23 in the lens head 26. If there is a transparency on the worktop 11 (not shown in the drawing) with an image content in the form of a label etc., this image content is projected via the lens 26 and the deflection mirror 27 onto an approximately vertical projection surface, which is also not shown in the drawing.

The rattle: 1 is held in its extended position by the catch 33, held by the spring 34, resting against the flats 31 and 32 of the arms 4 and 7. If the working projector 2 is to be folded into its transport position shown in Figure 2, the coupling piece 13 must be moved to the right using the handle 35. In doing so, the force of the spring 34 pushing the catch 33 against the flats 31 and 32 of the arms 4 and 5 is overcome and the lock is released. Since the arms 4 and 7 are operatively connected via their interlocking teeth 29 and 30, both parallelogram halves 3 and 6 of the folding arm 1 evenly follow the movement of the coupling piece 13 to the right. As a result, the projection head 19 moves downwards without changing its horizontal position. The movement takes place due to the forced guidance of the two parallelogram halves exactly in the optical axis of the lens 26 downwards into the position shown in Figure 2. During folding, the compression springs 37 and 39 counteract the weight of the projection head 19 and thus prevent the projection head 19 from falling downwards. The compression springs 37 and 39 are advantageous-

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e.g. designed as gas pressure springs and thus provide additional damping of the movement. In the transport position of the working projector 2, the mirror 27 is pivoted downwards and is not visible in Figure 2 of the drawing.

If the working projector 1 is to be moved to its projection position

brought, the 'projection head 19 on the hands' 24 is pulled upwards. Oa the compression springs 37 and 39 so t

are arranged to bear the weight of the projection head 19 H

counteract, only a very small amount of force is needed to move upwards |

ne actuation force is required. If the compression springs are 37 %

and 39 are designed as compression springs, also occurs at %

the upward movement additionally a dampening of the movement f.

The projector can therefore be operated very easily with just one hand. Once the extended end position of the folding arm 1 is reached, the catch 33 locks this position, as already described above.

Of course, the catch 33 does not have to be arranged in the coupling piece 13, but it is also possible to provide a catch on the bracket 12 and on the connecting piece 18, for example. It is important that both parallelogram halves 3 and 6 are locked. Furthermore, it is possible to provide tension springs in the parallelogram halves 3 and 6 instead of the compression springs 37 and 39 in a different arrangement, which counteract the weight of the projection head 19 and the folding arm 1.

Since the movement of the projection head 19 takes place in the optical axis of the lens 26, it is possible, for example, to provide a further locking position on the folding arm 1 for an intermediate setting of the projection head 19 for a DIN A 5 project. The focal length of the lens 26 is then adjusted to the smaller distance between the projection head 19 and the worktop 11, for example by means of an auxiliary lens.

Claims (6)

w» Protection claims 1. Folding arm for the projection head of work projectors, characterized in that the folding arm (1) is designed as a double parallelogram arm, the lower parallelogram half (3) of which is articulated to the work plate (11) and the upper parallelogram half (6) of which is articulated to the projection head (19), and that both parallelogram halves (3 and 6) are articulated to one another via a common coupling piece (13), and that a catch (33) is provided for both parallelogram halves (3 and 6), which holds the folding arm (1) in its extended end position in which the projection head (19) is in its operating position. 2. Folding arm according to claim 1, characterized in that the catch (33) is arranged in the coupling piece (13). 3. Folding arm according to claims 1 and 2, characterized in that the two parallelogram halves (3 and 6) of the folding arm (1) are connected to one another via toothings (29 and 30) in such a way that the movement of the two parallelogram halves (3 and 6) is positively controlled, i.e. occurs uniformly. 4. Folding arm according to claims 1, 2 and 3, characterized in that each parallelogram half (3 and 6) consists of two arms (4, 5 or 7 and 8) and that both arms (4, 5 or 7 and 8) are connected to one another via springs (37 or 39), the force of which is directed against the weight of the projection head (19). &igr; · «ta
· · · ■ 5. Folding arm according to claims 1 to 4, characterized in that the arms (4,5 or 7,8) arranged between i) ten springs (37 or 39) are designed as gas pressure springs are. 6. Folding arm according to claims 1 to 5, characterized in that a handle (3i>) for folding the folding arm (1) is provided on the coupling piece (13). •♦ · »fill ti I
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