EP1376764A2 - Multi-secable screw - Google Patents

Abstract

The screw is produced with a lower threaded section (16) and a number of hexagonal stages (30) separated by reduced sections (22) that fail at specific loads when torque is applied. The lower section (18) presses against an object. Disc sleeves may be fitted onto hexagonal sections to define which break section is to be used.

Description

The invention relates to a multiple shear bolt, with a cylindrical body, who has a thread on the outside and a head on the an end of the body that has engagement surfaces for a drive tool, wherein the screw has several axially separated predetermined breaking points, which are a row of shear planes.

Such shear bolts are known for example from EP-A-0 692 643 and are used for example in screw connectors to electrical cable conductors to join. In this context, it depends on the leader ends contact with a predetermined contact pressure to ensure a perfect to ensure mechanical and electrical connection.

In this context, shear bolts are well suited because they relate to specified ones Have the shear torques set. The head is torn off then that the screw is tightened to the specified torque has been generated and thus the desired contact pressure. At the same time reliably avoided that such a screw is tightened too much and Possibly crushed or damaged the conductor end of a cable conductor.

It should be remembered that the modern technology of screw connectors Usually requires that after mounting the appropriate contact screws no or only a very small screw protrusion outside the screw connector is available. Multiple shear bolts can meet this requirement comply with the corresponding design without further ado.

The conventional shear bolt according to EP-A-0 692 643 is designed that the shaft has a series of thread areas, which by cuts are separated from each other, which form predetermined breaking points in order to Specify shear planes.

However, such conventional shear bolts are not always satisfactory in practice, because they have separate, axially spaced threaded areas on the connection points can be easily damaged, so that the screwing in Shear bolt in a workpiece can be affected. In addition, at conventional shear bolts the mechanical resilience through cuts greatly reduced in thread.

The invention is therefore based on the object of a shear screw at the outset specified type, which has a robust construction and a reliable Function guaranteed in practice.

The solution according to the invention is a multiple shear screw type mentioned so that the body with a central pin non-circular cross-section, into which axially spaced radial recesses are incorporated are, and has one or more washers, which are attached to the pin and that the body has a continuous thread on its outside.

With the screw according to the invention, the task is performed in a satisfactory manner solved. The punctures can advantageously be used to produce the predetermined breaking points incorporated regardless of the thread on the outside of the body his. So there are no additional "edges" on any thread sections that can be damaged during handling. With A continuous, one-piece thread also ensures that the Screw works reliably even under high mechanical loads.

The number of axially spaced radial recesses and the corresponding plugged ones Slices can be chosen depending on the realities of practice to any number of shear planes at the predetermined breaking points to specify which are formed by the punctures.

In a development of the screw according to the invention it is provided that the punctures are designed as circumferential ring grooves. In this way it becomes even Shear of the screw favors when tightened and in operation a predetermined torque is exceeded.

In a development of the screw according to the invention it is provided that the punctures in the longitudinal section of the screw taper in a radial direction. The The respective shear plane can thus be specified exactly at which the screw is in operation to tear off.

In a development of the screw according to the invention it is provided that the punctures penetrate to different depths in the material of the pin in the radial direction. In this way it is achieved that the screw at the respective punctures then breaks off when the torque specified there at the respective point is exceeded. In particular, it can be specified at which point the screw easiest to tear off, and which predetermined breaking point is the last to tear off.

It is particularly advantageous if the punctures in the invention Screw have a flat bottom, which is substantially perpendicular to Central axis of the screw extends. In this way it is achieved that the screw forms the smoothest possible fracture surface when the screw is exceeded of a predetermined torque at the shear plane.

It when the punctures are designed such that the Screw on the shear planes formed by them at torques that gradually increase from the front end of the screw towards her head. If such a screw is used in operation and against a workpiece, for example tightened a conductor in a screw connector, this is achieved that the screw always breaks off at the appropriate point.

In another embodiment it is provided that the tear-off torques Gradually remove from the front end of the screw towards her head. This depends on the circumstances.

In a development of the screw according to the invention it is provided that the washers have an axial height that is equal to the axial distance between two adjacent radial recesses. This ensures that the screw after the tear-off forms a particularly smooth fracture plane.

It is particularly advantageous if the disks have a smooth top, which can be flat or convex on one side or concave on one side. If the Top is concave on one side, so you can achieve that the predetermined breaking point slightly in the area of the pin opposite the outer edge of the disc is sunk.

It when the top of the respective disc on the Outer edge is chamfered. In this way, after tearing off the Upper part of the screw no unnecessarily sharp edges on the remaining part the screw.

In a development of the screw according to the invention it is provided that the Screw at its front end has an annular plate that one Carrier for the attached discs forms. The plate forms on the one hand a stop for the respective discs and on the other hand forms the front Contact area of the screw.

It is particularly advantageous if the plate has the same diameter as that Has discs. Then the plate and the attached slices form a homogeneous one Unity, namely a cylindrical body that on the outside of the has continuous thread.

It is particularly advantageous if the plate with a crowned screw tip or another contact geometry is formed. Such screws are for electrical screw connector well suited. The screw tip can, for example the shape of a spherical cap, a tapered cone or a flat one Have the end face of a contact screw.

In a development of the screw according to the invention it is provided that the washers have an internal recess complementary to the tenon and with a press fit are placed directly on top of each other on the pin. This makes it a compact Design of the screw reached.

In principle, for the pin and the complementary inner recess Slices of any contour with a non-circular cross-section can be used. In practice However, it proves to be useful if a square is used as a non-circular cross-section or in particular a hexagon is used so that the pin and the washers come into positive engagement with each other.

It when the upper end of the pin the head of the Forms screw for the drive tool. Then no further processing of the Pin required, which forms the receptacle for the respective discs.

In one embodiment of the screw according to the invention it is provided that the pin has an outer edge at its upper end. In particular, can it is an external hexagon, so that conventional tools can be used.

In another embodiment of the screw it is provided that the pin on has an axially machined, central inner edge at its upper end, in particular a hexagon socket, so that conventional tools for actuation the screw can be used. Such an inner edge can additionally or alternatively to the outer edge, to give the fitter the choice of Tool.

• Bereitstellen eines Zapfens mit unrundem Querschnitt,
• Einarbeiten von axial beabstandeten radialen Einstichen in den Zapfen in vorgegebenen Abständen,
• Aufstecken einer Anzahl von Scheiben auf den Zapfen zur Bildung eines zylindrischen Körpers, und
• Einarbeiten eines durchgehenden Gewindes an der Außenseite des zylindrischen Körpers.

Furthermore, according to the invention, a method for producing a multiple shear bolt is specified, which has the following steps:

• Providing a pin with a non-circular cross-section,
• Incorporation of axially spaced radial recesses in the pin at predetermined intervals,
• Place a number of washers on the pin to form a cylindrical body, and
• Incorporation of a continuous thread on the outside of the cylindrical body.

In this way, radial punctures of the screw, which are axially spaced Form predetermined breaking points at the desired shear planes, in a protected form inside the screw housed while the screw itself on its outside has a continuous thread.

It when a pin with a radially projecting plate is particularly advantageous is used, which forms a carrier for the discs. The plate can be with specify the desired shape and dimension and at the same time form a support for the slices to be put on.

In a development of the method according to the invention it is provided that the disks with positive engagement on the pin and before incorporation of the thread can be fixed on it. This makes it particularly compact and homogeneous arrangement of the screw achieved.

Fig. 1

eine Seitenansicht eines Zapfens für eine erfindungsgemäße Schraube;

Fig. 2

eine perspektivische Seitenansicht, schräg von oben, auf den Zapfen gemäß Fig. 1;

Fig. 3

eine schematische perspektivische Darstellung der erfindungsgemäßen Schraube mit einem Zapfen und aufgesteckten Scheiben;

Fig. 4

eine schematische Draufsicht auf eine Scheibe für die erfindungsgemäße Schraube;

Fig. 5

eine perspektivische Seitenansicht einer Scheibe gemäß Fig. 4; und in

Fig. 6

eine schematische Seitenansicht einer erfindungsgemäßen Schraube.

The invention is explained in more detail below, also with regard to further features and advantages, using the description of exemplary embodiments and with reference to the accompanying drawings. The drawings show in

Fig. 1

a side view of a pin for a screw according to the invention;

Fig. 2

a perspective side view, obliquely from above, on the pin of FIG. 1;

Fig. 3

is a schematic perspective view of the screw according to the invention with a pin and attached washers;

Fig. 4

a schematic plan view of a washer for the screw according to the invention;

Fig. 5

a perspective side view of a disc of FIG. 4; and in

Fig. 6

is a schematic side view of a screw according to the invention.

1 and 2 of the drawings, a pin 12 can be seen as the base body for a multiple shear bolt according to the invention. The pin 12 has expediently a symmetrical structure with respect to the central axis 38. At the front End 14 of the pin 12 shows a circular plate 16 which its outside has a crowned screw tip 18, which, for example, as Spherical cap can be formed and the contact surface of a contact screw can form.

Detects between a head 20 on the top of the pin 12 and the plate 16 one has several radial recesses 22, which expediently have a flat bottom 24 to specify predetermined breaking points in the desired shear planes.

Fig. 3 shows a schematic representation of the entire screw 10 obliquely above, circular disks 26 being attached to the pin 12. In the 4 and 5 such disks 26 are shown schematically. You can see that these disks 26 each have an inner recess 28 which is non-circular Has cross section and is adapted to the non-circular cross section of the pin 12.

The height of the disks 26 is expediently such that it is the distance between two axially spaced recesses 22. Conveniently, are these dimensions, i.e. the axial distances between the punctures and so that the height of the disks is given uniformly, so that such disks 26th can be attached to the pin 12 in any order.

In the arrangement according to FIGS. 1 and 2 there are only three such punctures 22 provided so that two disks 26 are used for this. This number can but of course also be larger or smaller by a desired number of predetermined breaking points at the respective shear planes.

It is also possible to have two or more between two punctures 22 Disks 26 to use, but in practice it is useful if the number the washers 26 is not unnecessarily large in order to ensure good stability of the screw 10 achieve.

In the illustrated embodiment, the pin 12 has the shape of a uniform one External hexagon, which the disks 26 with a corresponding complementary hexagonal inner recess 28 receives, these with a press fit be plugged onto the pin 12. But it can also have any other contour non-circular cross-section can be used for the pin 12 or the washers 26, which are each complementary to each other to form a compact design to ensure the screw 10.

The top of the top disk 26 is in front of the last puncture 22 assigned to the head 20 of the shear screw 10, as can be seen in FIGS. 3 and 6 can.

As can be seen from FIGS. 3 and 6, the pin 12 forms with the attached Disks 26 a cylindrical body 32, on the outside of a continuous Thread 34 is incorporated.

In this embodiment, the head 20 is designed as an outer edge 36, in particular as an external hexagon, its outer contour having the same shape as the have underlying pin regions 30. Then the head 20 no longer needs to be processed separately.

If necessary, the head 20 can also have a smaller cross section. Of further it is possible to have a central inner edge in the upper end of the pin 12 incorporated axially symmetrically, in particular a hexagon socket, if this is desired.

The fitter can then use the tool to tighten the screw 10 to choose. It goes without saying that such an inner edge only one Occupies the area in the pin 12, which lies above the last shear plane 22. Such an embodiment is not specifically shown in the drawings.

The punctures 22 shown schematically in FIGS. 1 and 2 can be in some areas be provided, but are expediently designed as circumferential annular grooves and taper in a wedge shape in the longitudinal section of the screw in the radial direction towards the inside in order to precisely specify the location of the predetermined breaking points.

Depending on the desired shear torque on the respective The predetermined breaking point are the recesses 22 in the radial direction at different depths in the Material of the pin 12 incorporated. The punctures 22 have expediently a flat floor 24, substantially perpendicular to the central axis 38 of the Screw 10 to ensure a smooth fracture surface.

The dimensions of the recesses 22 are expediently designed such that that the shear torques from the plate 16 to the head 20 of the pin 12 gradually increase. This means that the lowest predetermined breaking point may break first or the predetermined breaking point adjacent to the head 20 when the screw 10 tightened against a workpiece and a torque is exceeded.

In another embodiment, the arrangement can also be such that the breakaway torques from the screw tip 18 at the front end of the Gradually remove screw 10 towards her head 20. Then it will be appropriate Attack surfaces in the form of an inner edge provided in the screw 10, to gradually tear off the corresponding screw components.

The disks 26 have a smooth, flat surface in the illustrated embodiment Top. However, this can also be convex on one side or concave on one side his. In the latter case it is achieved that the fracture surface on the pin 12 opposite the outer edge of the disc 26 is slightly sunk with the thread 34.

The upper side of the respective disk 26 is expediently on the outer edge chamfered. In this way, after tearing off such There are no unnecessarily sharp edges on the top of the shear screw could damage a sleeve, which could then be Screw connector is attached around.

With such a screw 10, the predetermined breaking points are those of the punctures 22 are formed, protected inside the finished screw 10 housed. The Screw 10 itself has a continuous external thread 34, as indicated in Fig. 6 is.

If such a screw 10 in operation in a workpiece with an internal thread is screwed in, for example a screw connector with an inserted Cable ladder, the screw 10 tears off at the corresponding shear plane, if a corresponding shear torque is exceeded. Then it breaks upper part of the pin 12 together with the disc or discs sitting thereon 26 from. The top of the underlying screwed disc 26 and the the radially inner region of the pin 12 then forms a largely flat and closed fracture surface.

To produce such a screw 10, a pin is provided, which has a non-circular cross-section, for example as an axially symmetrical external hexagon, which has a radially projecting stop at its lower end, the to serve as a support for the disks 26. Then 12 Appropriate radial recesses 22 are incorporated, with a predetermined number and penetration depth at the desired axial distances.

Then disks 26 with a complementary inner recess 28 become the outer one Configuration of the pin 12 plugged onto the pin 12 so that the cylindrical Body 32 according to FIG. 3 results. The aforementioned stop at the bottom The end of the pin 12 is advantageously designed as a plate 16, which is the same Diameter as the discs 26 has.

If the disks 26 are fixed, for example with a press fit, on the pin a thread is machined on the outside over the entire cylindrical body 32, especially curled or cut. This creates the end-to-end Thread 34 according to FIG. 6, during the puncture forming punctures 22 protected inside the screw 10 are housed.

Common metals or metal alloys can be used as material for the screw 10 are used, which are selected depending on the intended use. In special applications, such a screw can also be used entirely or partially made partially of plastic or some other insulating material, for example Ceramics.

LIST OF REFERENCE NUMBERS

10

Multiple shear screw

12

spigot

14

front end

16

Plate

18

screw tip

20

head

22

puncture

24

ground

26

disc

28

inner recess

30

peg regions

32

body

34

thread

36

outside Kant

38

central axis

Claims (19)

Multiple shear screw, with a cylindrical body (32) which has a thread (34) on its outside and with a head (20) at one end of the body (32) which has engagement surfaces (36) for a drive tool, the screw having a plurality of axially separated predetermined breaking points (22) which form a series of shear planes,
characterized in that the body (32) has a central pin (12) with a non-circular cross-section, into which axially spaced radial recesses (22) are incorporated, and one or more disks (26) which are attached to the pin (12) .
and that the body (32) has a continuous thread (34) on its outside. Screw according to claim 1,
characterized in that the recesses (22) are designed as circumferential annular grooves. Screw according to claim 1 or 2,
characterized in that the recesses (22) in the longitudinal section of the screw taper in a wedge shape in the radial direction. Screw according to one of claims 1 to 3,
characterized in that the recesses (22) penetrate into the material of the pin (12) at different depths in the radial direction. Screw according to one of claims 1 to 4,
characterized in that the recesses (22) have a flat bottom (24) which extends substantially perpendicular to the central axis (38) of the screw. Screw according to one of claims 1 to 5,
characterized in that the punctures (22) are designed in such a way that the screw breaks off at the shear planes they form at torques which gradually increase or decrease from the front end (14) of the screw to its head (20). Screw according to one of claims 1 to 6,
characterized in that the washers (26) have an axial height which is equal to the axial distance between two adjacent radial recesses (22). Screw according to one of claims 1 to 7,
characterized in that the disks (26) have a smooth upper side which is flat or convex on one side or concave on one side. Screw according to one of claims 1 to 8,
characterized in that the top of the respective disc (26) is chamfered on the outer edge. Screw according to one of claims 1 to 9,
characterized in that the screw has at its front end an annular plate (16) which forms a carrier for the attached disks (26). Screw according to claim 10,
characterized in that the plate (16) has the same diameter as the disks (26). Screw according to claim 10 or 11,
characterized in that the plate (16) is formed with a spherical screw tip (18). Screw according to one of claims 1 to 12,
characterized in that the disks (26) have an inner recess (28) complementary to the pin (12) and are press-fitted directly onto one another on the pin (12). Screw according to one of claims 1 to 13,
characterized in that the upper end of the pin (12) forms the head (20) of the screw for the driving tool. Screw according to one of claims 1 to 14,
characterized in that the pin (12) has an outer edge (36) as a head at its upper end. Screw according to one of claims 1 to 15,
characterized in that the pin (12) has an axially machined central inner edge at its upper end. Method of making a multiple shear bolt,
characterized by the following steps: Providing a pin (12) with a non-circular cross-section, Incorporation of axially spaced radial recesses (22) into the pin (12) at predetermined intervals, Place a number of disks (26) on the pin (12) to form a cylindrical body (32), and Machining a continuous thread (34) on the outside of the cylindrical body (32). The method of claim 17
characterized in that a pin (12) is used with a radially projecting plate (16) which forms a carrier for the disks (26). Method according to claim 17 or 18,
characterized in that the washers (26) are placed on the pin (12) with positive engagement and fixed thereon before the thread (34) is incorporated.

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