JPH038403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torque limiting screw lock stop having a threaded shank and a collar threaded onto the shank.

The usual purpose of a screw fastener is to tighten it to a sufficient but not excessive torque, and then to maintain the set torque and axial load on the shank body, such as the bolt to which the screw fastener is tightened. The key is to lock it in such a way. There are many examples of these in the prior art, one known stop is
This is George S. Wing's patent number 2940495 issued on June 14, 1960.

The Wing patent fastener uses a collar with a nut that is threaded on the inside surface and tightened onto the thread of the shank. Integral with the nut is a drive section, the driver engagement surface of which is connected to the nut portion via a shear section that has the lowest torque resistance of the three sections. When a predetermined torque is applied to this drive part, the shear part breaks and the drive part falls freely, leaving a correctly tightened nut on the shank. In this classic fastener, thread locking is achieved with a nut section that is first rolled round and rounded by engaging the outer thread, the resulting pulling back providing the desired locking effect. .

There is also a recently developed well-known Eddie Bolt. This forms a set of outer ribs on the nut which are engaged by the driver and the ribs collapse radially inward and are plastically deformed when an appropriate torque is applied to the ribs. The inward displacement of these ribs also causes the nut material to be displaced inwardly into engagement with the threads of the shank, thereby exerting a locking force. This outer rib is dependent on both the torque limit and the locking action. This results in an unfavorable critical relationship between these two effects.

The object of the present invention is to create a stop that can be locked without applying a set torque after the nut is set with a predetermined torque by means of a screw having a non-circular helix by inward displacement of the material of the rib and the nut part. It is to provide the ingredients.

A torque limiting screw lock stop according to the present invention includes an externally threaded shank and an internally threaded collar. At least one helix of the thread on the shank is non-circular. The collar has a nut part and a driving part. This drive part is shaped to be engaged by a screwdriver. A shear section is formed between the nut section and the drive section, which has the lowest torque resistance of the three sections. This shear portion breaks when a predetermined torque is applied between the two portions. The nut portion has an internal thread that engages a thread in the shank and an external rib that engages a swage tool. The swage tool deforms the ribs radially inward, displacing the material in the nut portion into a non-circular spiral, and locking the nut into the shank. But this is after the torque of the drive is released. The size and placement of the ribs is such that swaging of the rib to reduce diameter does not change the torque level when torqueing off the drive.

A preferred but optional feature of the invention is the provision of a plurality of the ribs.

A further preferred but optional feature of the invention is that the drive portion is formed such that its driver engagement surface is polygonal, and the rib is aligned with one of the corners or intersections of the polygon; The cam held by the driver is thus able to pass through the drive engagement portion, causing the drive surface to engage the drive portion and separating the cam and rib until the drive portion is torqued off from the nut.

In the present invention, the swage tool for setting a stop has a rotating body having a central axis and an open end, and the first
a first inner wall near an end thereof has an axially extending cam that engages the rib, and a second inner wall spaced apart from and coaxial with the first inner wall engages the driver engagement surface. and a regular polygonal drive surface with the cams arranged circumferentially in the center of one of the drive surfaces.

These and other features will become apparent from the description of the drawings below.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a collar 20 according to the invention. The collar has a hexagonal or polygonal drive portion 21 whose driver engagement surface 22 engages the drive surface of a suitable torque actuated tool. The driver engaging surfaces 22, 22, . . . meet at corner intersections 23, respectively. An unthreaded passageway 24 is formed axially through this drive and corresponds to the external threads of the shank body described below.

Nut portion 25 includes a metal body 26 of a suitable material having the desired strength and flexibility. It also has an internal thread 27 extending from the bore 28 at one end of the passage 29 towards the passage 24 of the drive part 21 . A stop body 30 having a plurality of stop surfaces 31 is provided on its outer surface to limit axial movement along a central axis 32 of the collar. It has at least one, preferably a plurality of ribs 33 on its outer periphery;
This rib 33 cams to lock the nut portion as described below.

The shearing section 35 is connected to the drive section and the nut section. It has a groove 36, which reduces the wall thickness of the collar and forms a minimum area in the torque of the three parts: drive part 21, nut part 25 and shear part 35. Therefore, in accordance with the principle described in Wing patent No. 2940495, upon application of a predetermined torque determined by the size, material and properties of the body in its groove 36, this drive part 21 is torqued off (torque-off); The nut portion is held at the predetermined torque required to shear the drive in groove 36. The wing patent is mentioned herein as a reference to indicate design standards and dimensions for torque-off.

The overall purpose is to tighten the nut against the shank body 40 to a predetermined torque. The shank body 40 is, for example, a shank 41 and its shank body 40.
A head 42 at one end and an external thread 4 on its outer surface.
It is a bolt with 3. At least one helix 45 (shown as helix 45 in FIG. 3) is non-circular. In fact, it is an advantage of the invention that this screw has at least one non-circular rounded projection 46 and is preferably trilobular shaped with three projections 46, 46, 46 as shown in the third figure.
This is the known thread shape shown in previous patents, such as patent no. 2940495. This can easily accept round screw nuts. Instead of this trilobular structure which can be formed by grinding a normal thread, a normal thread may be ground flat or a normal thread with a notch may be used. On the other hand, one non-circular helix is also sufficient to provide at least resistance to torque. Usually at least two or three non-circular spirals are formed. Also, they often do everything that way. At least one has an array of ribs against which to force the material. The material to be locked onto this screw is of course replaced by this non-circular spiral.

As best shown in FIG. 5, the joint 50 consists of a pair of workpieces 51 and 52 having a pair of parallel holes 53 and 54, through which the shank 41 is inserted and the head is placed on one side. abut and tighten the collar body downward against the other side.

As best shown in FIG. 6, a tool 60 is used to secure the joint. It has a bell-shaped opening 61 at one end and a hexagonal drive surface 62 formed on its inner surface. These are the drive section 2
1. A group of cams 63 are provided near this open end, which cams are arranged centrally on the driver-engaging surface and pass over the center of the driver-engaging surface on the drive section 21 to direct the tool into the drive section 21. Fully engage. The arrangement of the ribs at the intersections (corners) of the driver engaging surface 22 of the drive portion 21 allows this relationship.

Advancement of the tool axis is stopped by a stop surface 31, as best seen in FIG. A torque can now be applied to the collar body, while the rotation of the shank is limited by engaging it or the head at any position, the relationship between this element being shown in Figure 7. is well shown. When a predetermined torque is applied, the shear section breaks as shown in Figure 6, and relative rotational movement between the nut section and the tool section is then possible. This is the cam surface 6 of the tool.
3 into abutting engagement with the rib, the rib deformation process begins, and the nut material engages the non-circular helix in a radial inward direction. It rubs the rib material circumferentially as shown in FIG. Finally, this deformation is completed and the tool spins while being directed against the stop surface 31 and the tightening is completed.

This rib ensures that when the screw locking action exerts a torque on the nut portion, the torque is less than the torque when the nut portion is set and sheared. The torque level set by shear is therefore not disturbed by the locking action. These are completely independent of each other and can only occur sequentially.

This allows the invention to provide a torque-limiting screw locking stop that can be set to a predetermined torque and then locked in one operation, the locking and torque setting being independent of each other.

The invention is not limited to the embodiments shown, which are illustrative and not restrictive, and may be applied within the scope of the claims.

[Brief explanation of drawings]

FIG. 1 is a side view showing a half cross section of a collar according to an embodiment of the present invention, FIG. 2 is a side view of a shank body used in the present invention, FIG. 3 is a sectional view taken along the line 3-3 in FIG. The figures are a sectional view taken along the line 4-4 in FIG. FIG. 7 is a sectional view taken along the line 7--7 in FIG. 6, and FIGS. 8 and 9 are sectional views showing the screw locking operation of the present invention. 40...Shank font, 42...Head, 43...
...External thread, 45...Spiral, 20...Collar body, 2
5... Nut part, 21... Drive part, 35...
Sheared part, 27...Inner thread, 33...Outer rib,
24...inner passageway, 22...driver engagement surface.

Claims (1)

[Scope of Claims] 1. The shank body has a shaft, a head at one end, and an external thread adjacent to the other end, the thread having a plurality of spirals, and at least one of the spirals when viewed from the axial direction. the collar body is non-circular, the collar body having a nut portion, a driving portion and a shearing portion, the nut portion having an axially extending internal thread and at least one external rib integral with and projecting from an outer wall of the nut portion; The rib is arranged to be axially aligned with the non-circular helix when the nut is fully engaged with the shank body, and the drive portion has an internal passageway that is aligned with and larger than the internal thread. and having a non-circular driver engaging surface for receiving a driver for applying a torque to the drive portion, a shearing portion engaging the nut portion and the drive portion, and the drive portion applying torque to each of the portions. having the lowest resistance among the ribs so that they shear when a predetermined torque is applied to the drive portion, and the size and arrangement of the ribs are such that the swage tool displaces the rib material radially inward. the nut part locks into the helix by displacing the nut part into a non-circular helix when acted on, and only then does the drive part torque off so as not to increase the torque when the shear part breaks. and the material of the rib and nut portion is sufficiently flexible to allow the rib to swage inwardly. 2. A torque-limiting screw locking stop according to claim 1, wherein said non-circular spiral has at least one non-circular protrusion. 3. The torque-limiting screw lock stop of claim 2, wherein said non-circular spiral has three protrusions. 4. The torque-limiting screw lock stop according to claim 1, wherein said shearing portion has a groove forming a circular cross section of a size that is ruptured by said predetermined torque. 5 a plurality of said ribs, each rib having a cam-like edge so that when said swage tool rotates relative to said rib to displace said rib material in a radial inward direction and in a rotational direction; A torque-limiting screw locking stop according to claim 1, which facilitates progressive engagement. 6. The torque-limiting screw locking device according to claim 1, wherein a stop integral with said nut portion and protruding from said nut portion is provided in front of said outer wall to stop said swage tool at a predetermined axial position. 7 At least three driver engaging surfaces are arranged in a regular polygon, and the ribs are located at the intersections (corners) of the surfaces.
a tool having a cam aligned with and thereby engaging and swaging the rib can be advanced along the collar by the cam passing through the driver engagement surface in the angular space of the intersection;
This causes geometrically identical driver surfaces to engage the driver engagement surfaces in a torque-applying relationship such that the cams are aligned axially with the ribs but relative to each other until the shear portion ruptures. Claim 1 wherein the swage movement is prevented.
Torque-limiting screw locking fasteners as described in . 8 At least two ribs are at 180°,
8. A torque-limiting screw locking stop according to claim 7, wherein the non-circularity is eccentrically spaced 180° apart. 9. A torque-limiting screw locking stop according to claim 8, wherein the non-circular spiral has three protrusions. 10 The external threads of the shank body include a non-circular helix, and the internal passageway of the collar engages the external threads of the shank body. the nut portion has an internal thread, the drive portion has a passage sized to pass the thread, a shear portion connects the nut portion and the drive portion, and the shear portion has a minimum having a torque resistance of less than that which occurs while tightening said collar on a shank screw until said collar breaks at said sheared portion, and said breaking occurs while said nut portion is in said non-circular helix. A method of fastening a torque limiting screw locking device by applying torque and swaging.