DE2331568A1 - DEVICE FOR THE TEMPERATURE-DEPENDENT PRODUCTION OF A CONNECTION, IN PARTICULAR AN ELECTRICAL CONNECTION - Google Patents

Description

The invention relates to devices for preparing a compound _t in particular electrical connections, in which the force generated by an elastic member is used to establish a secure and good electrical connection.

The invention is particularly useful for forming an electrical and mechanical connection between one Conductor and a printed circuit suitable. So far, such connections were usually made by a plug connection made in which the circuit board fits into a slot and a conductive elastic Element with a conductive part of the plate

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holds. Such connections have several disadvantages. First, the panel does not get stuck in its inserted position held. Second, there is a risk that the electrical connection will deteriorate if the Contact is not activated,

A solder joint can be used to connect a conductor to a printed circuit board or circuit board. Such a connection is not "pluggable" ¹¹ and requires re-soldering each time the circuit board has to be removed or replaced. This disadvantage is particularly acute when many connections are to be made.

An improved connection device is described in Belgian patent 7855553. At this Device becomes a heat-recoverable metallic element used around an elastic element, for example around the legs of a forked element is arranged. A conductor is inserted between the legs and the heat-recoverable metallic element is shrunk, thereby pressing the legs inward and against the conductor. Such a device is somewhat limited in terms of the amount of movement and also relatively expensive to manufacture, so there is a need for an improved connector.

The invention relates to a device for establishing a connection, in particular an electrical connection, directed and has a first element that has a relatively large change in the force-displacement curve the temperature, and an elastic element which is arranged to this so that as a result of the alternating

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effect between the elastic element and the first element, the device has a position at a first Temperature and occupies another position at a second temperature.

In general, the first element and the elastic Element interacting so arranged that they have the tendency to act against each other and that elastic element preferably exhibits a substantially negligible change in strength with the Temperature, although this is not essential in principle. It is particularly preferable that the invention Devices have a "snap" action in their movement between positions at the first Temperature and the second temperature show. It is therefore preferable that one of the elements is advantageous the first element to have a non-proportional force-displacement behavior, so that the device between the snaps to both positions at a given temperature or over a given small temperature range. In this regard, a leaf spring loaded in the longitudinal direction is particularly suitable and advantageous as the first element. However, any combination that has a degressive characteristic (i.e. any combination, in which the force required to achieve a further spring travel is less than that required for a corresponding initial spring travel is necessary,) shows, can be used to achieve this "snap" effect achieve. For example, a conventional negative spring such as a plate spring can be used. These "Snap" effect is a very important feature of the devices according to the invention which are also used, for example, to open and close valves can"

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The first element, the relatively strong change in the force-displacement curve with the temperature, an Eblymeres or an elastomer of the known Be of the type that shows a relatively large change in modulus with temperature.

Preferably, however, the first element is made from a metal, in particular from a metal sometimes with "Memory" is made of the metal, which is a relatively large change in the Shows strength with temperature. Suitable metals are given, for example, in US patents 3,012,882 and 3,174,851 and in Belgian patents 703,649, 755,271 and 769,468. Particularly suitable Metals are alloys that contain approximately equal atomic proportions of titanium and nickel. You have used

2 borrowed an austenitic secant modulus of about 8437 kgf / mm (about 12 million psi) at 1/2% elongation and

2 a martensitic secant modulus of about 5 97.6 kp / mm (850,000 psi) at 5% elongation. This big difference in the secant module together with the strong one Change in elongation makes these alloys particularly useful for thermally actuable devices of the type described. With them there are comparatively large amounts for strength and movement each Unit of volume of the material achievable. It should also be mentioned here that tension and strain are exerted in this way must ensure that the material does not undergo permanent deformation to a significant degree when the load changes repeatedly. An initial permanent or plastic deformation is permissible, but must not occur when the load changes persist, since if this is the case the points between which the elements move each other Change load changes, which is undesirable.

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Other alloys showing a similar phenomenon are known and are examples of such alloys

by A. Nagasawa, 31 J. Phys. Soc. Japan No. July 1, 1971, Pages 136 - m7 indicated. Examples are cadmium gold, Copper-aluminum-nickel, indium-thallium, uranium-molybdenum and uranium-niobium, some of which alloys are mentioned in the aforementioned patents.

In general, the main change takes place in the force-displacement curve at the so-called transition temperature between the martensitic state and the austenitic one State takes place, the exact temperature depending on the exact composition of the alloy. In addition, since hysteresis sometimes occurs, the transition temperature may change depending on it change whether the metal is heated or cooled "

The devices according to the invention are particularly suitable for making permanent electrical connections, the most important forms of application being the making of such connections to circuit boards. For this Among other things, it is particularly preferable that the transition temperature of the metal that is used around the device a non-proportional force-displacement behavior to give, lower than the ambient temperature. This has several positive advantages. Most of all is it is then not necessary for the devices according to the invention to be equipped with a heating element must in order to bring about the conversion and thus the desired snap movement. This simplifies the devices and is also economically desirable. All that is required is a special cooling tool which can be used to cover a wide range of Devices in a state before commissioning

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bring a lower temperature. In some cases it can be beneficial to use a heating tool to To help complete the conversion, however, even in these cases a separate heating tool can be used can be used over a wide range of devices.

Second, choosing a material with a low transition temperature becomes a necessity the use of high temperatures is avoided. Aside from the obvious benefits of avoiding high temperatures it should be mentioned that in the devices according to the invention, in which the strength of the first element When used at ambient temperature, the tendency of metals to turn out to be at high temperatures relax, is essentially avoided. Therefore, the devices can have high interface pressures on the manufactured Maintaining contacts in spite of the fact that the establishment of contact automatically creates a high tension is brought into the material, which is prevented from fully assuming its high temperature form. Quite surprisingly, the devices according to the invention can be used easily and many times be reused if the temperature cycle is maintained because the material of the first element is not becomes permanently deformed or "fixed" when contact is made. For this reason, too, the inventive Devices are reused in a situation different from that in which it was used first. In other words, if they are to make contact with, for example, a thick circuit board was used, it can easily be followed by a thinner circuit board can be reused. This surprising and desirable

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worth property cannot be increased when the transition temperature is high.

A third advantage of using materials of high strength at ambient temperature is that this strength can be used to create the contact force. In other words, the material is not only used to actuate a second element that generates the force. For this reason, the contact forces achieved with the devices according to the invention are far higher than those that arise with conventional resilient connecting devices, despite the fact that the shape and dimensions of the devices according to the invention. necessarily have to be similar to those of conventional resilient connecting devices. In particular, it is important that the amount of movement is approximately the same for the two types of connecting devices. Conventional springs are made as thick as possible and as compatible with the amount of movement required. Since stiffness increases with the cube of the thickness, the required movement, along with an elastic limit of 1% or less in conventional metals, seriously limits the contact forces that can be achieved. In the preferred devices according to the invention, however, the conventional spring is only used to generate a relatively low pretensioning force which, when heated, is overcome by the force of the other element, which shows a temperature-dependent force-displacement curve. The force in the latter element is generally three to five times greater than the biasing force, giving a total contact force that is two to four times that which a corresponding conventional resilient connection

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Device shows.

It follows from this that the invention provides a temperature-dependent Device was created that has a first stable state at a temperature and a second assumes stable state at a different temperature and which is reusable even if it safe contact at relatively high temperatures can maintain. The two elements made up of materials · with different strength / temperature relationships are arranged in counteracting manner so that a bend of the second spring element can cause the first element to bend. When the temperature of the device is changed, the change in the spring characteristic of at least the first element has an overall movement result. If the first element is made of a "memory" metal, especially made of an alloy of titanium and nickel, a connecting device is obtained that operates at a high temperature can be operated. It should be mentioned here, however, that by a suitable choice of the respective materials and when appropriately designed, the devices of the present invention can be used in many different environments can be.

The invention is described in more detail below, for example in connection with the accompanying drawing demonstrate:

1 shows a side view, partly in section, of a device according to the invention;

Fig.IA is a graph showing a typical

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«A

desirable force-displacement curve for the device according to Fig. 1;

2 shows a side view, partly in section, of a second device according to the invention;

3 shows a side view, partly in section, of a third device according to the invention;

4 shows a side elevation of a first spring element, which can be used in a device according to the invention;

5 shows a side elevation of a second spring element, which can be used in a device according to the invention, and

6 shows a side elevation of a third spring element which is used in a device according to the invention can be.

In the device shown in Fig. 1, a cantilever spring 20 is provided with a curved end which is attached to a leaf spring member 21 loaded in the longitudinal direction. The spring 20 is through an opening used in a base 22. The spring element 21 is in the spring 20 by a stop 25 and a recess 26 held. The stop 25 also holds the spring 20 in the base 22.

The element 21 is made of a material that has a relatively low modulus at low temperatures but has a higher modulus at a high temperature,

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e.g. at ambient temperature, and the spring 20 is made of a material that is relatively has high modulus at low temperatures. At low temperatures, the device tries one Take up position, as it is indicated for example by the dash-dotted lines. When the temperature increases, the longitudinal force exerted by the element 21 also increases, so that this is extends into the position shown in full lines. If a circuit board 2 3 between the Device and the base 22 is placed, a firm contact between the circuit board and the Contact point 24 of the spring 20 made when the element 21 has a temperature at which it has a relatively high strength.

The device shown in Figure 1 provides a particularly effective temperature actuated device for one reason which is not easily recognizable. This reason concerns the spring characteristic of element 21. Although that Element 21 essentially has the shape of a leaf spring, if it is not loaded near its center point, but instead only in the longitudinal direction. The fact that the element 21 is so loaded, it exerts a relatively great force in a longitudinal direction when it is almost straight. In other words, it requires one relatively large force to deform the element 21 from its relaxed position, while once it is partially deformed, less force must be exerted to cause further deformation. Therefore, in contrast to most springs, the load / travel ratio or the stiffness is not constant, but rather changes depending on the amount of spring travel. Different

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expressed, it will be with most feathers when the Force is applied over the spring deflection, a straight line Line obtained, while a curved line results in a leaf spring loaded in the longitudinal direction.

If the right combination for the spring characteristics of the Springs 20 and 21 is chosen, it is possible to create a device that is relatively small Temperature change in the open position or "snaps" into the closed position.

One method of achieving this "snap" effect is in choosing an element with a spring characteristic, which has a vertex. In other words, the spring characteristic should reach a maximum, at least to that some part of decreasing steepness follows.

A typical spring characteristic for the first element is shown in FIG. 1A. A device with a snap action is obtained when the second element is connected to the first element so that the spring deflection of the first Element is on the left side of the vertex when the device is in a first stable state, and on the right side of the apex when the device is in its second stable position. Several forms of devices show a force-displacement curve with a somewhat negative slope.

Although a leaf spring loaded in the longitudinal direction is a particularly simple method of achieving this "snap" effect other non-linear springs can also be used. For example, a disc spring can be designed so that it has a strongly non-linear spring characteristic. Furthermore, if the ratio of the

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Height to thickness (h / s ratio) of the disc spring is correct is chosen (an example is a disc spring with an outside diameter of 12.5 cm (5 "), an inside diameter 6.25 cm (2 1/2 "), a thickness of one millimeter (0.040") and an h / s ratio greater than about 2.0 ^ the spring characteristic have a vertex, the to can be used to produce a snap action. See, for example, Kachine Design by J.E. Shigley McGraw-Hill, 1956, which on page 237, Fig. 7-15, spring characteristics for a number of different disc springs shows.

The device shown in Fig. 2 has a forked spring 30 with a leg 31 which is connected to a contact point 32 is provided. A longitudinally loaded element 33 is in grooves 34 and 35 of the spring 30 held. The spring 30 is held in an opening 36 in the base 37.

In order to bring about a movement of the device, the temperature of the device according to FIG. 2 is first reduced in such a way that that the element 3 3 requires only a small force in order to bring about a spring deflection. If the Spring 33 is made, for example, from an alloy with larger proportions of titanium and nickel, the Temperature can be reduced in order to bring the titanium-nickel alloy into its martensitifsehe phase. Through this the force exerted by it is reduced, thereby weakening it with respect to the spring 30, which then the element 3 can deform 3 into a position as shown by dash-dotted lines. The cooling down can for example by spraying with a low-boiling liquid that is pressurized has been done, using suitable cooling liquids

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Te met luoromethane, chlorotrifluorine than and trifluoromethane are. If necessary, the cooling can be done by contact with ice, liquid nitrogen or the like.

A circuit board 38 is then placed against part of the base 37 and the temperature of the device is then increased to increase the force exerted by element 33, which then causes spring 30 and the contact point 32 can be brought into the positions shown by the solid lines. In this Position it can exert a relatively large force against the circuit board 38, since the spring 33 occupies an almost straight position.

In contrast to the devices shown in FIGS. 1 and 2, the device according to FIG. 3 closes against one Object when the leaf spring-shaped element is in its position of low 'strength. Cantilever Tongues 40 and 41 are passed through a base 42 and an element 43 is inserted into grooves 44 and 4 5 of the Springs 40 and 41 held. The springs 40 and 41 are made of a material that is relatively shows strong change in the spring characteristic with temperature, while the element 43 from a conventional Material, for example spring steel, is made. When the temperature of the device after Fig. 3 is such that the element 4 3 is in its state high strength is located, the element 43 pushes the springs 40 and 41 apart in the dash-dotted lines in FIG drawn position. When the temperature is changed so that the characteristics of the springs 40 and is relatively high with respect to the module of the element 43, the device includes in the with full

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solid lines drawn position. Therefore, if an object 46 is between the contact points 47 and 48 the springs 40 and 41 is used, this is held in the manner shown.

Various spring configurations are shown in FIGS. 4-6. These springs can be used in the devices of Figs. 1-3. Although it is advantageous that the element analogous to element 21 of Figure 1 have a non-linear spring characteristic, this is not essential since the device will still be operable if the element has a constant spring characteristic. Although in the description of the devices according to FIGS. 1 and 2 it was indicated that the elongate leaf spring-shaped element consists of a material whose modulus changes significantly with temperature, the device can also be manufactured if the element which corresponds to the element of FIG 1 corresponds to _{y is} made of a material that has a spring characteristic that is relatively constant with temperature. The other spring should then be made of a material whose modulus changes significantly with temperature. For example, if the device of 'Fig. 1 is made so that the spring 20 is made of a titanium-nickel alloy, the device would seek the position shown in solid lines in Fig. 1 when the spring 20 is in its Low modulus condition. In a similar manner, the device according to FIG. 1 would strive to seek the position shown in FIG. 1 with dash-dotted lines when the spring 20 is in a state with a relatively high module.

It is important to note that the movements brought about in the devices according to the invention are not

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require that a change in size or length takes place in one of the spring elements. It's a change in the spring characteristic, which brings about a movement instead of a change in dimension. Distinguish in this way the inventions according to sen devices in the form of bimetallic elements, the mode of action of the different Expansion or contraction with the Temperature depends. Changes in the properties, for example the secant module, bring about a change in the characteristic of a spring with itself. For example, the alloys have approximately equal atomic proportions of titanium

2 and nickel usually have a secant modulus of about 597.6 kgf / n (about 850,000 psi) at 5% elongation in the mart

2 sitic phase and a secant module of about 8 4 37 kp / mm

(12 million psi) at 1/2% elongation in the austenitic Phase.

The devices of the present invention have the potential advantage that they are made entirely of metals so that they can be made to withstand great temperature extremes. The titanium-nickel alloy remains solid at high temperatures. For example, the modulus of elasticity of the titanium-nickel alloy at 600 ^° C. is about 14 million and the strength of many spring steels remains high ^{at 600 ° C.}

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Claims (1)

Jb Claims Device for establishing a connection, in particular an electrical connection, characterized by a first element which has a relative
shows strong change in the force-displacement curve with temperature and an elastic element that increases
the former is arranged so that by the interaction between the elastic element and the first element, the device assumes one position at a first temperature and at a second
Temperature a different position. 2. Device according to claim 1, characterized in that that the element shows a comparatively strong change in the force-displacement curve with a comparatively minor one Shows temperature change. 3. Apparatus according to claim 2, characterized in that the relatively strong change in the force-displacement curve at a temperature or over a
Temperature range does not take place higher than the ambient temperature. Device according to claims 1-3, characterized by " -16- 309885/0941 indicates that the elastic element is a substantially shows negligible change in strength with temperature. 5. Device according to claims 1-4, characterized in that the spring characteristic of one of the Elements is nonlinear. 6. Apparatus according to claim 5, characterized in that the spring characteristic of one of the elements at least has a negative slope over part of it. 7. Device according to claims 1-6, characterized in that the spring characteristic curve by egg Vertex goes through. 8. Device according to claims 5-7, characterized in that said element is the first Element is. 9. Temperature activated device that provides relatively substantial movement with relatively minor Can run change in temperature over a critical temperature range, characterized by - 17 - 309885/0941 J » a first element with a non-linear characteristic, part of which has a negative slope over at least shows a portion of the usable travel range of the device; and a second spring element which is arranged relative to the first element so that a bending movement of the second Spring element a bending movement of the first element on one side of the apex of the spring characteristic to the other side of the apex, at least one of the elements being made of a material is that a relatively large change in the spring characteristic can experience with a relatively minor change in temperature. 10. The device according to claim 9, characterized in that the first element is made of a material is that a relatively large change in the spring characteristic with a relatively small change in temperature can experience. 11. The device according to claim 9, characterized in that the second element is made of a material that is a relatively large change in the spring characteristic with a relatively small change in temperature can experience. 12. Device according to claims 1-11, characterized in that the first element made of a metal is. - 18 - 309885/0941 13. The apparatus according to claim 12, characterized in that the metal is an alloy with larger Proportions of titanium and nickel. 14. The device according to claim 13, characterized in ^ that the alloy contains approximately equal atomic proportions of titanium and nickel. 15. Device according to claims 1-11, characterized in that the first element consists of a polymer or made of a non-metallic elastomer. 16. Device according to claims 1-15, characterized in that the first element is one in the longitudinal direction loaded leaf spring is. 17. The device according to claim 16, characterized in that the leaf spring can assume almost a columnar shape, 18. Device according to claims 1-15, characterized in that that the first element is a plate spring. 19. Device according to claims 1-18, characterized in that the elastic element at least has two legs. - 19 - 309885/0941 20. Apparatus according to claim 19, characterized in that that the first element is arranged between the legs mentioned. 21. The device according to claim 20, characterized in that the elastic element is a cantilever spring having a curved end and the first member is disposed transverse to the curved end. 22. For a cryogenic temperature sensitive device for making good electrical contact at normal operating temperatures which, however, can move to interrupt the to enable electrical contact when cooling below a critical temperature is indicated by a first element that is made of a metal that has a significant change in the force-displacement curve in the vicinity of the critical temperature mentioned, it is possible to find out which first element is an in leaf spring loaded in its longitudinal direction; a second element made of one material is, which has a relatively uniform force-displacement curve in the range of motion of the device has, which second element has at least one movable leg and with the first element is connected so that a bending movement of the second element to a bending movement of the first element Consequence. - 20 - 309885/0941 23. Device according to claims 1-22, characterized in that that the element with a temperature changer lent Force path shows a higher strength in its a higher temperature state. Device according to claims 1-23, characterized indicates that at least one of the elements is a Has a projection or the like that can establish a good electrical contact. 25. Leaf spring loaded in its longitudinal direction, characterized in that it is made of a metal is that a relatively large change in strength for a relatively small change in temperature learns. 26. A method for establishing a connection, in particular an electrical connection, characterized in that an object or objects • is or are brought into contact with a device according to claims 1-2H and then the temperature reduction is brought about which is necessary to bring about a movement of the device. 27. The method according to claim 26, characterized in that that the temperature change is a rise in temperature is. - 21 - 309885/0941 28. The method according to claim 26, characterized in that the first element of the device has a higher Shows strength at high temperatures. 29. The method according to claims 26 and 27, characterized in that that the object is a circuit board. - 22 - 309885/0941