EP0159372B1 - Tap or collector brush for potentiometers, path-length meters and similar devices - Google Patents

Abstract

Tap or current collector for rotary or linear potentiometers, displacement pick-ups, variable resistances, brushes/collector junctions of electric motors, etc., wherein the tapping part on which the slider elements as such are mounted and which performs a relative movement with respect to the tapped path or collector carries the slider elements having individual resilient and freely movable slider fingers, at least in the contact area proper, and which are mounted on a mounting block in such a manner, relative to the sense of displacement, that irrespective of the sense in which the tap moves at any time, one of the slider elements is always pushed, and the other one is always pulled so that even the influences on the tapped or transmitted electric signal of dynamical effects developed by high accelerations are compensated. Further, the individual slider elements are pre-bent along their longitudinal extension so that they follow a pre-determined curve in the inoperative condition and assume a substantially straight shape when applied under resilient pressure to the path to be scanned, whereby the distance between the tap and the path can be minimized.

Description

State of the art

The invention is based on a tap or pantograph according to the preamble of claim 1. In a known sliding resistor with a tap of this type (DE-U-7 540 374) is in a rectangular, elongated housing as the bottom a plastic support plate for the parallel lying Resistance and collector track, while the slide forming the tap is guided by profile rails extending along the housing in such a way that parts of the slide are encompassed by the profile rails without play and a braking effect in the slide direction can be exerted. A sliding contact spring is mounted on or inserted into the slide, which has the shape of a rectangular frame in which the resilient track and the collector track make contacting spring arms project inwards out of the frame level. In order to achieve better contact with the resistance and the collector path, two spring arms are provided for the resistance path and the collector path, which are obviously arranged on the frame on opposite sides for reasons of contact, so that in each direction of movement of the slide always one of the assigned path contacting grinder arms are pulled and the other is pushed. This can be seen from the drawing of FIG. 2, that the spring arms assigned to each path to be tapped overlap in the middle, that is, they must form a short-circuit zone, with no further details being given about the precise design, articulation and type of contact .

Also known from DE-A-3 132 415 is a variable resistor, in which two wiper elements slide on a common resistance track in the opposite direction to one another, which slide with further wiper elements on mutually insulated collector tracks. The whole, in a simplified form, represents a kind of double potentiometer, the resistance path being common to both potentiometers, since the same potential relationships are permitted. Each of the wiper elements opens into a plurality of mutually separate elastic wiper fingers that slide on the associated path.

It is generally known to design taps or current collectors for rotary or linear potentiometers or high-precision displacement transducers in such a way that the individual wiper fingers sliding over the associated path or track are made of a suitable elastic material, usually a noble metal alloy, and can be moved individually and at the rear end in a common clamping, leading to the tap, stored and held. It is also possible to produce the individual grinder fingers by punching them out of a corresponding flat sheet metal part. The direct sliding contact area lying under spring pressure on the track or runway is formed by a suitable bending of the end of each grinder finger, which bending can also take place approximately at right angles with the formation of an end hook or a type of claw.

The illustration in FIG. 1 shows the state of the art in detail and with the aid of this illustration, the problems arising with such taps or current collectors are discussed in more detail below. The following explanations relate in particular to the design of a tap for a so-called displacement sensor, which is usually a linear potentiometer, which may also be very long (up to 2 m), which is used as an actual value transmitter on moving machine parts. Particularly in the case of high-speed machines, for example in the field of plastic injection molding, extreme demands are placed on such linear displacement transducers, which consist in the grinder being guided over the middle of the runway at very high speed (as a numerical speed specification, here is an average value of, for example, 10 km / Hour), whereby the grinder is pulled back at the respective end points under the influence of considerable acceleration values and guided in the opposite direction. Under all conditions and also in operations in which several hundred or thousand million cycles have to be carried out, the transmission of a completely faultless voltage signal by the displacement sensor must be ensured. In this context, it should first be pointed out that the following explanation of this special prior art is directed to a preferred field of application of such high-precision potentiometers or displacement transducers as actual value transmitters for linear displacements; the invention is of course not restricted to such an area of application and can preferably be used wherever similar problems arise in places where currents or voltages from stationary parts are to be transmitted to rotating or moving elements.

In FIG. 1, which represents the state of the art, the tap is designated as a whole by 10 - it consists of one here representative of all possible conceivable storage and assembly forms standing blocks 11, which can be driven by any machine part, the actual value adjustment must be represented by a highly accurate voltage signal, and from the actual grinder element, here consisting of a large number of juxtaposed, from one suitable precious metal alloy existing grinder fingers 12, which are attached at 13 to the bearing block 11. The resistance path, the potential of which is picked up by the tap during its movement and is usually to be transmitted to a parallel collector or return path, is designated by 14. The individual wiper fingers 12, which are arranged next to one another approximately in this way and can be arranged at a mutual distance, as shown in the view from below in FIG. 3, are bent at 15 and form a hook-shaped support or the actual wiper contact area, which is denoted by 16 and its lower surface slides on the resistance track. Assuming that the tap 10 first moves at a comparatively high speed in the direction of arrow A and, after reaching a predetermined reversal point, which can be formed, for example, by the position of the tap shown in FIG. 1, immediately with extreme acceleration in the opposite direction of the arrow B is torn around and moved, then at this moment of the action of the very high accelerations the grinder element tends to try to stand out against its own elastic spring pressure in the direction of the arrow C from the runway or path, if only because of the mass and inertial effects acting on the grinder element. This process takes place dynamically, of course, very quickly, but due to the necessarily asymmetrical mounting of the grinder element with respect to the two directions of movement A and B, there is an additional disadvantage, which arises when the tap with the highest acceleration from the direction of movement at the other reversal point B is reversed in the direction of movement A. Also again due to the mass or moments of inertia and still supported by the spring action of the grinder element, this then tries at the other reversal point to "dig" into the path, so to speak, according to the direction of the dashed arrow D, so that just at the reversal points Tapping movement Problems in the correct and clean illustration and reproduction of the tapped voltages can result.

Now it is precisely the turning points at which a particularly faithful reproduction of the tapped signal is absolutely necessary, for example if one only thinks of the use of such displacement sensors for machines for plastics processing, that is to say injection molding machines or the like. Such plastic injection molding machines have machine parts or tools that approach each other at considerable speed and whose flawless reproduction of the actual value is an essential prerequisite for damage-free and clean working of the machines. In the case of mold heads or mold halves approaching one another in plastic injection molding machines, the material is only injected at the last moment, immediately before the reversal points, where extremely high pressures occur and the tools are practically in contact, and it is precisely at these moments that the correct actual value position of the tools must be able to be determined with the greatest accuracy .

Further peripheral problems with the known taps resulted, for example, from the fact that, in order to apply the necessary spring tension to the grinder element, it forms a curved curve shape in the downwardly concave shape as shown in FIG. 1, which, as is easy to imagine can, this results if you put the ladder on the slope with the desired pressure and keep the stored block 11 horizontal. Due to this bulging of the wiper element resulting from the spring preload in the working position, however, the bearing block 11 must maintain a certain minimum distance, which is designated E in FIG. 1, from the surface of the web, so that the bulge does not, particularly when the end hook 16 processed slowly, came too close to the surface of the resistance track. However, a distance E that is as small as possible is desirable so that the comparatively high moment, which is otherwise developed due to this distance around the point of contact on the resistance track, is small. This relatively high moment in connection with the fact that the grinder element is pushed in one direction of movement, but pulled in the other, additionally contributes to asymmetrical working and possibly to a lift, to a rattling on the piste, to irregularities in the reproduced Voltage u. Like at.

It is therefore the object of the present invention to ensure, in the case of a tap or pantograph of the type mentioned at the outset, that even under the action of the highest accelerations, the tapped potential is reproduced flawlessly and without interference and the sliding behavior of the tap on the track, the slope, the Collector or the like is flawless, no chatter marks are set and as few tilting moments as possible are developed.

Advantages of the invention

The tap or pantograph according to the invention solves this problem with the characterizing features of the main claim and has the advantage that a perfectly lifelike image of the actual movement of the respective machine element can be achieved in the form of a voltage, in particular also in the particularly trouble-prone reversal points of the potentiometer or displacement transducer on which a number of dynamic effects take effect due to the extremely high accelerations acting on them. The invention succeeds in mastering these dynamic effects on the one hand or eliminating them by mechanical measures, and on the other hand ensures that the actual movement of the machine element is properly mapped even if dynamic residual influences remain.

The opposing arrangement of at least two grinder elements ensures that at each possible point on the path at least one of the grinder elements is always pulled, the other is pushed, whereby in the respective end regions or reversal points, although both grinders seem to be practically stationary for a short moment , act on both completely different dynamic effects, but in such a way that one of the wiper elements is always able to offer the desired actual value voltage without any problems or errors.

It is also particularly advantageous in the present invention that the novel shape and design of the tap or pantograph permits working cycles of several hundred or thousands of millions, that is to say in a number which was previously thought to be completely unthinkable. In the same way, the tap according to the invention withstands speeds and accelerations that would have led to complete destruction in a few hours in the case of earlier taps.

Advantageous further developments and improvements of the attack or pantograph specified in the main claim are possible through the measures listed in the subclaims. The pre-tensioned, bent shape of each grinder element in the idle state is particularly advantageous if it is not placed on the web to be contacted. Due to the characteristic bending curvature in retirement, when the elastic contact force is maintained on each longitudinal part element δl of the grinder, a force results which overall means that in the installed state of the tap, the grinder elements run practically completely straight from their clamping point to the bent end hook, So that it is possible to get significantly closer to the resistance path with the tap, to drastically reduce the distance of the clamping leading to tilting moments, vibrations, digging in or braking or to increased friction losses, and the displacement forces acting on the tap, which are ultimately in the contact zone between the end hook and the resistance track, as close as possible to them. Long-term tests have shown that this can be used to control a large number of vibration problems and dynamic effects that previously led to serious damage.

drawing

• Fig. 1 ein Ausführungsbeispiel eines Abgriffs oder Stromabnehmers in einer schematischen Teilschnittdarstellung, die den Stand der Technik wiedergibt,
• Fig. 2 ein Ausführungsbeispiel vorliegender Erfindung in einer Seitenansicht,
• Fig. 3 das Ausführungsbeispiel der Fig. 2 in einer Ansicht von unten, in beiden Fällen im nichteingebauten Ruhezustand der Schleiferelemente, und
• Fig. 4 den erfindungsgemäßen Abgriff mit seinen Schleiferelementen im eingebauten Zustand, in welchem die Endhaken der Schleifer auf der Piste unter Druck aufliegen.

Embodiments of the invention are shown in the drawing and are explained in more detail in the following description. Show it:

• 1 shows an embodiment of a tap or pantograph in a schematic partial sectional view, which represents the prior art,
• 2 shows an embodiment of the present invention in a side view,
• Fig. 3 shows the embodiment of FIG. 2 in a view from below, in both cases in the non-installed idle state of the grinder elements, and
• Fig. 4 the tap according to the invention with its grinder elements in the installed state, in which the end hooks of the grinder lie on the slope under pressure.

description of Embodiments

The basic idea of the present invention is to design the tap in such a way that, regardless of the direction in which it is moved over the assigned path to be contacted, a grinder element is always pulled at the same time and at the same time a grinder element is always pushed out of its clamping, making it a full one constant balancing of the above-mentioned dynamic effects.

In FIGS. 2-4, subcomponents and elements that are identical to FIG. 1 are provided with the same reference numerals, supplemented by a comma at the top.

In the exemplary embodiment of a tap 10 'shown in FIGS. 2 and 3, the block storing the tap or grinder components is designated 11' - it has a greater length here, which extends in the longitudinal direction of the tap movement, and can consist of a lower base part 11a 'and a mounting leg 11 b running at right angles thereto' be provided with holes 20 for attachment. To clarify the term, it should be noted that in the following the entire movable element is referred to as tap, including the bearing block, which is moved along the resistance path or the element to be contacted. The bearing block 11 'then carries individual grinder elements 12a' and 12b ', which in turn are again formed from individual grinder fingers which are usually connected in one piece to one end region. The wiper fingers are collectively designated 21 (see FIG. 3).

As the illustration in FIG. 2 shows, the tap according to the invention is designed in such a way that two grinder elements 12a ', 12b' mounted against one another or arranged in opposite directions are at least provided if one initially only focuses on the means for scanning an assumed resistance spell. A concrete exemplary embodiment will be discussed with reference to FIG. 3. The exact assembly of these two grinder elements 12a ', 12b' takes place in such a way that they contact a common transverse line to the usual direction of movement in the installed state on the resistance track or other slope or collector, which is already necessary so that of both grinder sub-elements 12a ', 12b' same potential is detected. Therefore, in the exemplary embodiment shown in FIG. 2, the respective clamping points of the grinder elements face away from one another and have a predetermined distance in the direction of displacement, the grinding surfaces of the end hooks lying on a common line. That this is not the case in the illustration in FIG. 2 is because FIG. 2 shows a tap or pantograph in the idle state, that is to say in the unmounted position, in which at the same time another essential inventive feature is implemented, which is followed immediately is received.

The two mutually facing grinder elements 12a ', 12b' are in any case so mounted on the carrier block 11 ', which is preferably common here, that no matter in which direction of the double arrow AB the tap is moved, always one of the grinder elements 12a', 12b 'from its clamping point seen, pulled and always pushed one. The clamping can be designed as shown in Fig. 2, i.e. support plates 22 are provided for each grinder element, which are fastened to the base plate 11 a 'of the support block 11' by means of two screws 23 (see also FIG. 3) and to which in turn the punched-out final shape of each grinder element is there, where this is still continuous is integral, such as by spot welding, as shown at 24. The reason for the separate attachment of each wiper element 12a ', 12b' to an additional carrier plate lies mainly in the fact that the material of the wiper elements forming the individual wiper fingers 21 is an expensive precious metal alloy, the main components of which are palladium, platinum, silver and gold (technical name Paliney no 6 or 7).

The individual wiper elements 12a ', 12b' are punched out of narrow alloy strips in such a way that the cuts forming the recesses between the wiper fingers 21 are made up to relatively close to the fastening region 24 on the support plate 22, so that each wiper finger is largely self-supporting and can react elastically compliant.

At the other end region, a small remaining distance is hook-shaped, approximately at right angles and, in this respect, is bent to form a type of claw as end hook 16, the lower surface of which then slides on the assigned path. Since this sliding surface is uniform in cross-section, a certain amount of wear and tear can be accepted without the data changing significantly. At the same time, the free spaces formed by the recesses between the individual wiper fingers result in the possibility that loose material or abrasion on the resistance track does not lead to a lifting of the contact surface of the wiper fingers, but rather can be pushed aside.

In Fig. 3 you can see the juxtaposition of the individual grinder fingers 21 of each of the grinder part elements 12a ', 12b', to which there are then two further slider part elements 26a, 26b, which can be mounted on the same, electrically conductive support plate 22 in the same way and so simultaneously contact the grinder for the return path or collector path that runs parallel to the resistance path when carrying out the invention as a linear displacement sensor. It is otherwise not necessary that the bearing block 11 ', on which the mutually mounted, bilateral Schleiferhä _l ften 27a, 27b are mounted as shown in FIG. 3, is electrically conductive, it can therefore consist of a suitable plastic or the like .. , because the return path wiper elements 26a, 26b also touch with their contact surfaces of the end hooks 16 'a common point of the return path and thus ensure that the (identical) potential provided by both resistance path wiper elements 12a', 12b 'in the parallel connection of these two Grinder elements can then be tapped at the connection of the return path.

It has already been mentioned above that the deflection of the individual wiper fingers resulting from the required elasticity and spring stiffness of each wiper finger and in order to obtain the necessary contact pressure of the wiper surface on the end hook 16 is disadvantageous, both with regard to storage and distance to the resistance track and also with regard to the dynamic effects resulting from this unfavorable arch shape in the assembled working state.

A preferred embodiment of the present invention therefore consists in the fact that, according to the striking and possibly exaggerated representation of FIG. 2, the individual wiper fingers and thus all parallel wiper fingers follow this shape in their entirety in the rest state, are bent in a pre-curved curve shape, in such a way that that they are concave with respect to the resistance path on which they later slide, ie are bulged upwards.

If such a tap is placed on the resistance track with the wiper element configuration shown in FIG. 2, as shown in FIG. 4, then the pressing pressure results in an essentially completely linear design of the individual wiper elements, so that one can also use the Entire tap, so that can approach the bearing block 11 'very close to the resistance valve 14' or the other part to be contacted, switches over tilting moments, pulls practically on the grinder elements at the point at which they then also with the sliding contact the surface of the resistance track 14 'are also braked again, if one disregards the very small and exaggerated distance of the end hook, so that it is possible to have a balancing and calming effect on the dynamic tap operation and of course also the inertia or Influence of mass reduced when tapping after the prior art (Fig. 1) occurs at the reversal point of the movement

It can also be seen that by applying the tap to the resistance track, of course, the backbend of the grinder elements 12a ', 12b' which are pre-bent in the idle state takes place in such a way that, of course after the spacing has been adjusted beforehand, the respective end hooks 16 have a completely congruent position 'on the piste results, as also shown in Fig. 4

To adjust the distance between the two grinder parts 27a and 27b relative to one another, the procedure is otherwise such that, before installation, a device having a transparent surface is pressed onto the grinder elements from below until the distance that the tap is to take up to the resistance track is reached and then carry out the axial adjustment on one of the wiper parts 27a or 27b by means of the fastening screws 23 until all the wiper part elements are matched in the aligned position of the bent end hooks 16 '.

A further advantageous embodiment of the present invention then consists in that the individual wiper fingers resiliently resting on the web with pressure bear a common layer or covering of an elastomer or a silicone rubber, in any case a rubber-like material with internal friction, in common covering on at least one side, so that the individual free spring movement of each grinder finger is still possible, but is damped by the other fingers and by the action of the elastomer itself, so that resonances or jumping or rattling of the grinder fingers do not occur.

Another feature inherent in the following invention in a particularly advantageous manner is that, if one first takes a look at the state-of-the-art illustration of FIG. 1, with increasing wear of the end region of the end hook 16 that grinds on the runway, this simultaneously results in how 1 in dashed lines at 16 'in FIG. 1, a shift in the voltage tap point on the resistance track is also the result, while on the other hand, in the double-grinder design according to the invention, a falsification of the measurement result caused by wear is excluded. This is because, even with the double grinder design, wear of the end regions of the hooks 16 'cannot be ruled out, but the grinders that are worn in each case shift in the opposite direction, so that the voltage tapping point does not change on average. Of course, it should be pointed out that the relationships shown in FIGS. 1 and 4 at 16'a, just described, are exaggerated in the illustration for better understanding.

Claims (9)

1. Tap or current collector for rotary or linear potentiometers, displacement pickups, sliding resistors, brushes/collector junctions, in particular in electric motors, with at least two wiper members sliding on the tapped path, which each comprise at least one wiper finger resting resiliently on the path and in which case the wiper members with respect.to the reversible sliding direction of the tap are mounted in opposition to each other on the tap so that for a given direction of movement, one of the wiper members is always pushed by its mounting and the other is pulled, characterised in that the at least one wiper finger (21) of each wiper member (12a', 12b') is bent forwards from its rear mounting up to the attachment point of an end hook (16') in the direction of the path (14) to be tapped so that with corresponding adjustment of the height of the wiper member mountings over the path, the contact points formed by the wiper fingers (21) on the path lie on a common line extending transverse to the sliding direction of the tap.

2. Tap according to Claim 1, characterised in that each wiper member (12a', 12b') comprises a given number of parallel, resilient wiper fingers (21), whereof the end producing the respective contact point wiping on the tapped path (14) is formed by the bent end hook (16').

3. Tap according to Claim 1 or 2, characterised in that the at least two wiper members (12a', 12b') simultaneously contacting each path to be tapped are attached to a common small support block (11') so that the end parts which connect the wiper fingers to each other in one piece and which are remote from the end hooks of the individual wiper fingers (21), are mounted remote from each other and the end hooks (16') of the wiper fingers (21) are located opposite each other.

4. Tap according to one of Claims 1 to 3, characterised in that in each case two wiper members (12a', 26a, 12b', 26b) are fastened in pairs and in an electrically conducting connection to the common support block (11'), thereby contacting in each case a resistance path (14) as well as a collector path of a linear displacement pickup extending parallel thereto and the other pair of wiper members respectively being located opposite and likewise connected to each other in an electrically conducting manner.

5. Tap according to one of Claims 1 to 4, characterised in that for each pair of wiper members (12a', 26a; 12b', 26b) a common support plate (22) is provided, to which the one-piece end regions of each wiper member are attached, preferably by spot welding, in which case at least one of the support plates (22) is attached to the support block (11') by means of releasable fastening means (23) for the purpose of axial adjustment.

6. Tap according to one of Claims 1 to 5, characterised in that each wiper member consists of a longitudinal plate of precious metal, from which the individual wiper fingers are punched with the formation of mutual recesses (25), whereby the recesses (25) extend almost to the respective mounting region (24) of each wiper member on the support block (22) so that each wiper finger may react in a resilient manner independently of the others.

7. Tap according to one of Claims 1 to 6, characterised in that in the relaxed state of rest including the resilient tension, the bent curvature of the individual wiper fingers (21) is constructed so that when placed on the respective path (14) to be tapped, each wiper finger assumes a virtually linear shape from its rear mounting to the attachment point of the end hook.

8. Tap according to one of Claims 1 to 7, characterised in that the cross-sectional surface of each end hook (16') of each wiper finger (21) forming the actual wiping contact is constant as far as the bending region and transition to the longitudinal wiper finger so that even with a higher degree of wear, no variations occur as regards the longitudinal ranges of resistance covered per passage.

9. Tap according to one of Claims 1 to 8, characterised in that the individual wiper fingers (21), with the exception of the actual wiper contact region, are coated, covered or overlaid with an elastomeric material having high internal friction, thereby connecting them to each other, so that the relative free mobility of each wiper finger (21) is retained, but is highly damped.

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