Microswitch and test system

Abstract

The invention relates to a microswitch, comprising a cylindrical sleeve in which a piston is arranged in an axially movable manner. A contact pin is arranged in the piston in an axially movable manner. The contact pin interacts with two mating contacts which are fixed at a distance from each other in the bottom of the sleeve. The movement of the contact pin is supported by two springs. A return spring is disposed between the bottom of the sleeve and the piston and moves the piston to an initial position when the microswitch is not actuated. A buffer spring is arranged between the contact pin and the piston actuation cap and is responsible for gently placing the contact pin onto the mating contact. The ball is disposed between the buffer spring and the contact pin. In order to buffer the movement of the contact pin only before being placed on the mating contact for a long time, the buffer spring has a greater spring force than the return spring. The microswitch can be constructed with a robust metal sleeve and can operate despite no insulation between the piston and the sleeve. The two mating contacts also result in a large contact area and an improved guidance of the contact pin.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application number "201810625279.0" and invention name "Microswitch and test system" filed by applicants "Lisa Drexelmayer GmbH" and "Fitest Test Equipment GmbH" on June 18, 2018. Technical Field

[0002] The invention relates to a microswitch and a testing system for testing the presence of a component, such as a cable harness. Background Art

[0003] When manufacturing cable harnesses, multiple components must be fixed on the line. If a component fails or cannot be installed in the correct position, the subsequent repair is very troublesome because the installation of the cable harness in technical equipment such as a motor vehicle does not coincide with the manufacturing site and no repair equipment is available. Therefore, it is important to test the cable harness during or after manufacturing.

[0004] A test system for testing cable harnesses comprises at least one component receptacle in which a microswitch is arranged. The component receptacle is positioned on a construction plate for producing the cable harness in such a way that a component, the presence and position of which is to be tested, can be pushed into the component receptacle. This movement actuates the microswitch. The resulting signal is then evaluated and confirms the correct installation of the component on the cable harness. If the component is removed from the component receptacle, the microswitch assumes its initial position again. After many years of installation of such cable harnesses, thousands of switching operations have occurred and considerable wear and tear has occurred.

[0005] Known micro switches (e.g., TS-32 from Salecom Electronics Co., Ltd.) utilize contact connection via the housing of the micro switch and a second switchable contact cooperating with a movable contact tip. However, this requires that the housing be insulated internally from the switchable contact, and it has been shown that this insulation wears out over time. In addition, the switching point of the micro switch is highly dependent on tolerances, so that the force applied via the inserted component and the distance traveled must be precisely measured in order to prevent erroneous switching. This is disadvantageous in terms of manufacturing technology.

[0006] Micro switches are generally known from the prior art. Document DE 20 2014 003 924 U1 discloses a spring contact switching pin for testing a test piece. In addition, utility model DE 20 2009 012 411 U1 describes a switch spring contact pin, utility model DE 20 2007 007 095 U1 describes a spring contact pin, in particular a switching pin, and utility model DE 295 06 688 U1 describes a switch with a switching bridge. Document DE 198 08 060 A1 describes a limit tester, and document DE 3609 127 A1 describes a key switch. Patent DE 27 16 192 C2 discloses an electric switch. Summary of the invention

[0007] The object of the present invention is therefore to provide a microswitch and a test piece holder which have an increased service life while taking up little space and defining switching points with the smallest possible tolerance range.

[0008] The microswitch according to the present invention comprises a cylindrical sleeve, in which a piston is arranged in an axially movable manner. A contact pin is arranged in the piston in an axially movable manner. The contact pin cooperates with two mating contacts fixed in the bottom of the sleeve at a distance from each other. The movement of the contact pin is supported by two springs. The return spring is arranged between the bottom of the sleeve and the piston and moves the piston to the initial position when the microswitch is not actuated. The buffer spring is arranged between the contact pin and the piston actuation cap and is responsible for gently placing the contact pin on the mating contact. The spherical piece is arranged between the buffer spring and the contact pin. In order to buffer the movement of the contact pin only shortly before it is placed on the mating contact, the buffer spring has a spring force greater than the return spring. The microswitch can be constructed with a stable metal sleeve and can work despite the lack of insulation between the piston and the sleeve. The two mating contacts also lead to a larger contact surface and improve the guidance of the contact pin. The buffer spring can also better set the switching point with a larger tolerance, because the electrical contact is maintained in a sufficiently long section during the compression of the buffer spring. It has been demonstrated that the microswitch of the present invention can achieve approximately 500,000 switching cycles.

[0009] According to an advantageous improvement of the present invention, a first inclined portion is introduced, which is located in the inner space of the sleeve and opens toward the sleeve bottom. Thus, the piston is centered in the sleeve and a buffering stop occurs when the piston returns to the initial position.

[0010] It is also advantageous if a second bevel is introduced into the inner cylinder of the piston, which is open toward the actuating cap. This allows the contact tip to be centered when it moves in the piston. Advantageously, the sleeve, the piston and the contact pin are formed rotationally symmetrically along the axis of movement of the piston and the contact pin.

[0011] A further development of the microswitch provides that a retaining plate made of plastic is fixed to the sleeve bottom, in which the mating contacts are embedded. The insulation of the mating contacts relative to the sleeve made of metal is achieved in a structurally simple manner by the retaining plate.

[0012] Advantageously, the actuating cap is made of metal so that it will only show minor wear and no damage during thousands of contacts with the component pressed onto it. For easy mounting on the piston, which is advantageously made of plastic, the actuating cap is press-fitted into the piston. The bearing surface of the actuating cap projects beyond the central cylinder, which has a larger diameter than the inner cylinder of the piston.

[0013] If the actuating cap projects laterally beyond the piston and the piston projects axially beyond the sleeve, the sleeve provides a stop for the piston and the actuating cap which prevents damage to the contacts (contact pin and mating contact).

[0014] In order to achieve a good electrical connection during switching, it is advantageous if the surface of the contact is designed to be of high quality. It is therefore proposed to introduce a contact tip which can be inserted into the contact pin on the side facing the mating contact. The contact tip should be made of a metal coated with a precious metal, the contact pin should be made of plastic, and the contact tip should be press-fitted into the contact pin. This allows for simple assembly of the contact tip and good functionality at low cost through material selection.

[0015] In order to fix the sleeve base, it is advantageously provided that the sleeve is bent over at the sleeve base after the mounting plate has been inserted, ie deformed in such a way that the sleeve base and the mounting plate are firmly connected.

[0016] If a ball is arranged between the buffer spring and the contact pin, the contact pin can be oriented at any time. This allows the contact pin to maintain a slight wobble / tremor, resulting in a uniform contact, low friction and a constant spring force. The ball is advantageously made of a non-conductive material, such as plastic or glass, in order to remain potential-free even if the entire piston is made of metal.

[0017] The described microswitch according to the invention is constructed as follows in the test system according to the invention:

[0018] The test system comprises a component receiving part, which has a cavity in the shape of the component to be received. The microswitch is inserted into the cavity. Usually, a plurality of component receiving parts and a plurality of microswitches are provided in order to comprehensively test a cable harness or other complete technical equipment. The evaluation device of the test system is connected to the mating contacts of the microswitch and can thus evaluate the electrical signals generated by the switching and verify the presence and correct positioning of the component. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] An advantageous embodiment of the present invention is explained below with reference to the accompanying drawings, wherein:

[0020] Figure 1 A first variant of a microswitch according to the invention is shown,

[0021] Figure 2 A second variant of the microswitch according to the invention is shown, and

[0022] Figure 3 A test system according to the invention is shown. DETAILED DESCRIPTION

[0023] The above figures are only exemplary illustrations and are only used to illustrate the present invention. The same or the same function components are provided with the same reference numerals throughout the text.

[0024] according to Figure 1 The first microswitch 1 according to the invention comprises a cylindrical sleeve 2 with a narrowed and open neck from which a piston 3 protrudes. The piston 3 is also cylindrically shaped and is movably arranged in the sleeve 2. There is only a small gap between the sleeve 2 and the piston 3. The piston 3 can be pressed in the sleeve 2 in the direction of the sleeve bottom 21, so that the piston 3 and the sleeve 2 are separated at a first inclined portion 8 open to the sleeve bottom 21, which connects the neck of the sleeve 2 with a wide central base. When the piston 3 returns to the initial position due to the return spring 6 arranged at the sleeve bottom 21 or between the retaining plate 10 installed at the sleeve bottom 21 and the piston 3, the first inclined portion 8 causes the piston 3 to move in a centered and damped manner in the sleeve 2. Figure 1 The piston 3 is shown in an initial position in which the electrical contact is open.

[0025] The piston 3 is made of plastic, for example POM, while the sleeve is made of, for example, nickel-plated brass. The retaining plate 10 is also made of plastic, for example PEEK.

[0026] The return spring 6 is a helical spring, formed of high-quality steel, and has a diameter slightly smaller than the diameter of the piston 3. Two mating contacts 51, 52 embedded in the retaining plate 10 and a contact pin 4 are arranged within the periphery of the return spring 6. The contact pin 4 acts centrally between the two mating contacts 51, 52, and a contact tip 11 is press-fitted in the contact pin 4, which is conically shaped toward the later contact point as well as the mating contacts 51, 52. Therefore, a relatively large area of ​​contact is obtained by the conical surfaces of the contact tip 11 and the mating contacts 51, 52. The mating contacts 51, 52 and the contact tip 11 are, for example, gold-plated brass contacts. The contact pin 4 is made of plastic.

[0027] The contact pin 4 is arranged in the piston 3 in an axially movable manner. However, this mobility is only important when the contact tip 11 has already been placed on the mating contacts 51, 52. When the piston 3 moves further in the direction of the sleeve bottom 21, the contact pin 4 does not move in the same way, but performs a relative movement relative to the piston 3 in the opposite direction of the movement of the piston 3. This achieves a gentle placement of the contact tip 11 on the mating contacts 51, 52 and reduces its wear. This also results in a better defined landing point.

[0028] The buffer spring 7 is responsible for this gentle seating, which is arranged between the contact pin 4 and the actuating cap 31 which is press-fitted into the piston 3. The buffer spring 7 is a helical spring made of high-quality steel and has a smaller diameter than the diameter of the inner barrel of the piston 3, in which the contact pin 4 can move axially. The gap between the inner barrel of the piston 3 and the contact pin 4 is very small, and the second bevel 9, which is open toward the actuating cap 31, centers the movement of the contact pin 4 and ensures a gentle stop of the contact pin 4 in the piston 3. The spring force of the buffer spring 7 is greater than the spring force of the return spring 6, so that when pressure acts on the actuating cap 31, the piston 3 and the contact pin 4 first perform the same movement against the force of the return spring 6, and the buffer spring 7 is only compressed a little later after the contact tip 11 has been seated.

[0029] Another stop is determined by the shape of the actuating cap 31 and the piston 3. The edge of the actuating cap 31 protrudes laterally (i.e. perpendicularly to the piston axis) beyond the central cylinder of the actuating cap 31 and beyond the piston 3. Thus, when the actuating cap 31 is actuated, if the piston 3 is pressed sufficiently deep into the sleeve 2, the edge of the actuating cap 31 rests on the neck of the sleeve 2. This stop thus prevents mechanical damage to the microswitch 1. The switching point of the microswitch 1 can already be reached after 0.80-1.10 mm. The electrical contact is maintained until the maximum actuation travel of about 2.7 mm has been traveled.

[0030] Figure 2 FIG. 2 shows an alternative second microswitch 1 according to the present invention. Figure 1 The first micro switch quite.

[0031] However, a special contact tip 11 is omitted here, and the contact pin 4 (here made of gold-plated brass) is placed directly on the mating contacts 51, 52. The shape of the mating contacts 51, 52 and the shape of the tip of the contact pin 4 are also conical, but they are more Figure 1 More strongly rounded and less sharply tapered in the.

[0032] The mating contacts 51 , 52 embedded in the holding plate 10 are each connected to a respective cable 14 , and an insulating portion 13 in the form of a heat shrink sleeve is provided on the portions of the mating contacts 51 , 52 protruding from the sleeve bottom 21 and the cables 14 .

[0033] In order to better orient the contact pin 4, a ball 12 made of insulating material (here glass) is inserted between the contact pin 4 and the buffer spring 7. The contact pin 4 has a recess on the side facing the buffer spring 7 for receiving the ball 12 in the contact pin 4.

[0034] according to Figure 2 The microswitch 1 is in the switched state, the contact pin 4 is electrically connected to the two mating contacts 51, 52, so that a current can be measured, which indicates that the microswitch 1 is actuated, that is, the actuating cap 31 made of solid metal is pressed in at least to the switching point.

[0035] Figure 3 The use of the invention according to Figure 1 or Figure 2 A test system for a microswitch 1. The microswitch 1 is installed in a cavity 41 of a component receiving portion 40 of the test system. The cavity 41 is formed in this case so that the cavity corresponds to the shape of the component to be received and therefore has the component to be tested in its presence and correct position. If the component is pressed into the component receiving portion 40, the microswitch 1 is also actuated, and a signal is generated by connecting the mating contacts 51, 52 via the contact tip 4 or the contact pin 4. The mating contacts 51, 52 are connected to an analysis device 42, which can thus detect correctly installed components. The analysis device 42 is usually connected to a plurality of microswitches 1 in a plurality of component receiving portions 40, and can therefore test the entire cable harness by a plurality of tests in parallel.

[0036] Reference numerals list

[0037] 1 Micro switch

[0038] 2 sleeves

[0039] 3 Piston

[0040] 4 contact pins

[0041] 6Return spring

[0042] 7. Buffer spring

[0043] 8First inclined portion

[0044] 9 Second inclined portion

[0045] 10. Hold Plate

[0046] 11Contact tip

[0047] 12 spherical parts

[0048] 13 Insulation

[0049] 14 Cables

[0050] 21 bottom

[0051] 31 Actuating cap

[0052] 40 component receiving portion

[0053] 41 Cavity

[0054] 42Analysis and processing device

[0055] 51,52 matching contacts

Claims

1. A micro switch (1), comprising: A cylindrical sleeve (2) made of metal, A piston (3) is arranged in the sleeve (2) in an axially movable manner. A contact pin (4) is arranged in the piston (3) in an axially movable manner, Two mating contacts (51, 52) fixed in the bottom (21) of the sleeve (2) at a distance from each other within the circumference of the return spring (6), a return spring (6) located between the sleeve bottom (21) and the piston (3), which moves the piston (3) to an initial position when the microswitch (1) is not actuated, a buffer spring (7) located between the contact pin (4) and the actuating cap (31) of the piston (3), which buffer spring enables the contact pin (4) to be gently placed on the mating contacts (51, 52), a spherical member (12) arranged between the buffer spring (7) and the contact pin (4), in, The buffer spring (7) has a greater spring force than the return spring (6).

2. The microswitch (1) according to claim 1, wherein: The micro switch has a first inclined portion (8) of the sleeve (2), which is open toward the sleeve bottom (21).

3. The microswitch (1) according to claim 1 or 2, wherein: The micro switch has a second inclined portion (9) located in the inner cylinder of the piston (3), and the second inclined portion is open toward the actuating cap (31).

4. The microswitch (1) according to any one of claims 1 to 3, wherein: The microswitch has a holding plate (10) made of plastic, which is fixed to a sleeve bottom (21) and in which mating contacts (51, 52) are embedded.

5. The microswitch (1) according to any one of claims 1 to 4, wherein: The actuating cap (31) is made of metal.

6. The microswitch (1) according to any one of the preceding claims, wherein: The actuating cap (31) protrudes laterally from the piston (3), and the piston (3) protrudes axially from the sleeve (2), so that the sleeve (2) provides an axial stop for the piston (3) by stopping the actuating cap (31).

7. The microswitch (1) according to any one of the preceding claims, wherein: The microswitch has a contact tip (11) which is inserted into a contact pin (4) facing toward a mating contact (51, 52).

8. The microswitch (1) according to claim 7, wherein: The contact tip (11) is made of metal coated with a precious metal, the contact pin (4) is made of plastic, and the contact tip (11) is press-fitted into the contact pin (4).

9. The microswitch (1) according to claim 4, wherein: After the sleeve (2) is inserted into the retaining plate (10), the sleeve bottom (21) is bent over.

10. The microswitch (1) according to any one of the preceding claims, wherein: The spherical member (12) is constructed of a non-conductive material.

11. The microswitch (1) according to any one of the preceding claims, wherein: The ball (12) is constructed of plastic.

12. The microswitch (1) according to any one of the preceding claims, wherein: The spherical member (12) is constructed of glass.

13. The microswitch (1) according to any one of claims 10 to 12, wherein: The entire piston (3) is made of metal.

14. The microswitch (1) according to any one of claims 1 to 12, wherein: The piston (3) is made of plastic and the actuating cap (31) is press-fitted into the piston (3).

15. The microswitch (1) according to any one of the preceding claims, wherein: The contact pin (4) has a recess on the side facing the buffer spring (7) for receiving the ball (12) in the contact pin (4).

16. A test system, the test system comprising: A component receiving portion (40) having a cavity (41) in the shape of a component to be received, The microswitch (1) according to any one of claims 1 to 15, wherein the microswitch is arranged in the cavity (41), An evaluation device (42) is connected to mating contacts (51, 52) of the microswitch (1).

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