Patent Application
20250003445
The present invention relates to a pawl nut having a securing element.
To axially secure topper elements of a shaft, for example a wheel hub having a wheel bearing on a drive shaft joint of a motor vehicle, a caulking nut can be screwed onto the shaft to prevent unintentional loosening of the attached topper element. For this purpose, the shaft has a thread-shaft section, in particular a type of axle journal with an external thread. Known shafts also have radial recesses, particularly in the thread-shaft section. After the caulking nut has been tightened and the topper element has been braced on the shaft, in particular the wheel hub has been braced on the axle journal in a form-fitting and non-rotating manner, the caulking nut itself can be deformed by radial force applied to the recesses of the shaft. Alternatively or additionally, a securing element, in particular a clamping ring, can be used, which secures the caulking nut in the recess by plastic deformation, in particular caulking, in a form-fit and non-rotatable manner in both directions.
A fastening method by means of plastic deformation of the caulking nut or a securing element is comparatively complex and requires a large number of work steps, particularly manual work, and special tools. In addition, the caulking nut can only be loosened with great effort due to the form-fit connection to the shaft, for example for repair and/or replacement purposes. Moreover, plastic deformation and an associated weakening of the material can lead to corrosion problems later on.
Alternatively, a type of cotter pin or locking bolt can be used as a securing element, this cotter pin being inserted into a recess in the shaft in the form of a bore and a radial slot in a castle nut in order to fix the castle nut on the shaft in a screwed-on state. Such a castle nut with cotter pin is known, for example, from DE 69 106 939 T2. The castle nut usually has 6-8 slots having an angular spacing of 45° to 60° in the circumferential direction to secure it. In order to bring such a slot into radial overlap with the recess, in particular the bore, within the shaft, the castle nut may be overtightened or there may be too much axial play in relation to the topper element. An incorrect torque on the castle nut can lead to damage to the shaft itself and/or a topper element, particularly if the shaft is subjected to alternating loads during operation. Installing the cotter pin is also time-consuming and labor-intensive. Furthermore, reuse of a disassembled castle nut cannot be ruled out, which is why there is a potential safety risk if the castle nut itself is damaged.
In particular since the aforementioned securing elements also secure the caulking nut or castle nut along a tightening direction in a form-fit manner in addition to securing it in a loosening direction, the caulking nut or castle nut cannot be readjusted after the fastening process. This can lead to an increase in the axial play to the topper element and potential damage during operation of the shaft, particularly due to a changing load.
DE 10 2010 053 595 A1 shows a pawl nut having a closed retaining ring which forms a first mutual pawl indentation with the pawl nut on an outer side. On an inner side, the retaining ring forms a second mutual pawl indentation with a shaft. The first pawl indentation is sawtooth-shaped, with the indentation flanks of the first pawl indentation being intended to slide against each other in a tightening direction. In this context, it can be assumed that during rotation along the tightening direction, the indentation flanks of the outer indentations of the retaining ring can become deformed and/or worn by being in contact with the indentations of the pawl nut. This wear can influence a fixation against the tightening direction and in particular lead to an unintentional loosening of the pawl nut. Furthermore, the deformation of the indentation flanks can require a considerable amount of force, which prevents simple, particularly manual, assembly. In particular, the production of deformable indentation flanks of the retaining ring, for example in the form of flared sheet metal strips, requires increased manufacturing precision in order to form a non-rotating pawl groove. In addition, deformable indentation flanks have reduced strength, for which reason individual indentation flanks can break off and the pawl nut can become loose, particularly under continuous cyclic loading.
CN 105 257 670 discloses a non-releasable anti-theft screw device having a locking screw, a locking nut and a securing element, a recess being formed in a thread bar of the locking screw and a slot being formed in the locking nut; a group of locking latches being disposed on the interior wall of the slot; the securing element having a fastening end and a resistance end; the securing element being able to inserted loosely in the slot, the securing element facilitating a locking of the screw device in the assembled state.
CN 2 646 463 Y discloses a lockable screw connection having a screw, a nut and a securing element. The screw is equipped with a vertical groove; upper and lower surfaces of the nut are equipped with jagged protrusions at intervals along the circumference; the inner diameter of the securing element is equipped with a conical embossing, which engages in the vertical groove of the screw. In the assembled state, the jagged protrusions of the nut jam with the surface of the securing element and facilitate a cost-efficient theft protection.
U.S. Pat. No. 4,824,303 A discloses a locking-wedge device for fastening a printed circuit board. The device comprises an oblong center wedge having inclined surfaces and two end wedges, which abut against opposite inclined surfaces of the center wedge. The two end wedges are connected to each other via a screw which engages in a threaded hole in the removed end wedge. A friction nut is affixed to a part of the removed end of the screw, the part protruding beyond the removed end wedge, and the device is configured such that it has a pair of low-friction abutting surfaces between the nut and the removed end wedge. This ensures that the friction moment exerted on the nut by the end wedge is exceeded by the friction moment exerted on the nut by the screw when removing the screw entirely.
The object of the present invention is therefore to propose a pawl nut which, while avoiding the problems known from the state of the art, is particularly easy to assemble and manufacture and at the same time ensures a high degree of operational safety.
This object is attained by the features disclosed herein.
Advantageous embodiments are also disclosed herein and/or are the subject matter of the dependent claims.
According to the invention, a pawl nut having a securing element as an axial securing mechanism for a topper element of a shaft is proposed, in particular a bearing of a gear shaft or a wheel bearing of a Cardan shaft, the pawl nut being screwed on a, in particular frontal, thread-shaft section of the shaft in a tightening direction in order to axially brace the topper element on the shaft along a screwing axis in the mounted state, the securing element having an engagement section which engages in a recess of the shaft and holds the pawl nut along a loosening direction in the mounted state, in particular in a form-fitted manner. In this context, the pawl nut mounts the securing element along the screwing axis, the pawl nut being twisted in one direction along the tightening direction in relation to the securing element.
Furthermore, the invention intends that the pawl nut together with the securing element forms pawl indentations, which mutually engage along the loosening direction, in the radial direction and the securing element can be inserted in the pawl nut and its pawl indentations along the screwing axis, the securing element being formed as a securing ring which is open in the circumferential direction and is elastically deformable in such a manner on one side along the tightening direction that the pawl nut is rotatable along the tightening direction in relation to the securing element, in particular in a sliding manner.
Preferably, the securing ring is elastically deformable in the radial direction.
Preferably, the recess in the shaft is formed along the screwing axis, in particular in the form of at least one longitudinal groove, in order to ensure guidance of the engagement section of the securing element while the pawl nut is being screwed on.
The invention has surprisingly recognized that by using a pawl nut with a securing element that can be twisted in one direction, the pawl nut for securing the topper element can be screwed onto the shaft independently and unhindered by the securing element and secures itself in an opposite loosening direction. No further work steps or special tools are required for this self-locking action. Due to the mounting of the securing element, it is adjusted linearly along the screwing axis together with the pawl nut. The pawl nut can therefore be screwed onto the shaft like an ordinary nut in a particularly simple manner, in particular without special tools and preferably by hand. Counter to the tightening direction and along the loosening direction, the pawl nut has a self-locking effect with the securing element, which is fixed in the circumferential direction in the assembled state, for which reason a loosening of the pawl nut is hindered or blocked by a preferably form-fit stop of the engagement element in the recess of the shaft.
In other words, in contrast to known caulking nuts or castle nuts with locking pins, the pawl nut can preferably screw itself in the tightening direction in a self-locking manner in the assembled state and at the same time lock along the loosening direction.
In a preferred embodiment, the pawl nut forms mutually engaging pawl indentations together with the securing element along the loosening direction, at least one of the pawl indentations being elastically deformable in such a manner that the pawl nut can be rotated along the tightening direction in relation to the securing element, in particular in a sliding manner. The elastic deformation of one of the pawl indentations can enable the pawl nut to rotate freely in one direction in the tightening direction, individual indentations of the pawl indentations sliding against each other or jump over each other while the pawl nut is being screwed on. In the opposite loosening direction, the pawl indentations engage with each other and thus prevent an unintentional loosening of the pawl nut and the bracing with the topper element in the assembled state.
Preferably, the pawl indentation and/or the elastically deformable securing element is designed such that the pawl nut can be screwed on manually along the tightening direction, in particular with a torque of approximately 1 Nm to 6 Nm. The pawl indentation is also preferably designed in such a manner that the engagement section acts as a kind of weakest link. In doing so, the pawl nut preferably can only be removed by destructively breaking off the engagement section of the securing element. The torque required for disassembly is particularly preferably between 70 Nm and 90 Nm, preferably 80 Nm. The shape and/or the material of the engagement section is preferably designed in such a manner, in particular having a lower hardness and/or strength, that the shaft is not damaged by the disassembly.
In a preferred embodiment, the pawl indentations of the pawl nut and the pawl indentations of the securing element are formed in a radial direction and the securing element can be inserted into the pawl nut and its pawl indentation along the screwing axis. In other words, the securing element is designed as a type of toothed disk, which preferably engages in an internal toothing of the pawl nut.
A radial pawl indentation is advantageous because in this arrangement, an elastic deformation can advantageously be formed by the securing element itself and not by individual web-shaped indentations. Furthermore, the securing element can move along the screwing axis in a guide section, the radial pawl indentation having a minimum contact pressure in order to prevent a loss of indentations. Movement of the securing element along the screwing axis makes it easier, in particular, to unscrew the pawl nut and engage the engagement section of the securing element in the recess of the shaft. The ability of the securing element to move along the guide section results in self-alignment of the engagement section in relation to the recess of the shaft.
In other words, in a further development, it may preferably be provided that the securing element is movable along the screwing axis in a guide section in order to facilitate engagement of the engagement section in the recess, the radial pawl indentation having a minimum contact pressure in order to prevent loss of indentation.
In a preferred assembly method, the pawl nut is screwed onto the shaft, the securing element along with the pawl nut being rotated around the screwing axis and adjusted along the screwing axis. If the engagement section is not aligned with the recess in the shaft, the engagement section will rest against a front of the shaft when it comes into contact with the shaft. A further rotation of the pawl nut leads to a relative displacement of the securing element with respect to the pawl nut within the guide section until the engagement section engages in the recess of the shaft, in particular as a spring-and-groove connection. Preferably, a length of the guide section is designed such that an engagement section of the securing element rotated by up to 180° relative to the recess can be brought into engagement for self-alignment and without bracing. In other words, the guide section acts as a kind of tolerance range along the screwing axis if the engagement section of the securing element is not aligned from the outset with respect to the recess of the shaft. Advantageously, this guide section enables particularly easy assembly.
In this context, the securing element can preferably be designed as a securing ring, which has a radial pawl indentation, is open in the circumferential direction and is elastically deformable, preferably in the radial direction. The elastically deformable securing ring is preferably designed in such a manner that the minimum pressure of the radial pawl indentation is ensured in the assembled state in order to prevent an indentation loss in the undeformed state. As soon as the pawl nut rotates along the tightening direction relative to the securing element, the pawl indentations slide against each other and deform the securing element in the radial direction and/or in the circumferential direction in such a manner that the pawl nut can essentially rotate unhindered and freely. Preferably, the rigidity of the securing element is such that the elastic deformation and rotation of the pawl nut can be operated manually by an operator. Advantageously, a ratchet-like rotation of the pawl nut in the tightening direction relative to the securing element generates an operating noise, in particular due to sliding and/or skipping pawl indentations, which can indicate to the operator that the pawl nut is functioning correctly and securely. In particular, a ratchet-like operating noise which characterizes a skipping of the pawl indentations indicates correct engagement of the pawl indentations. For example, a lack of minimum radial pressure of the pawl indentations would have an effect on the operating noise and weaken a ratchet-like noise characteristic; whereas a functional securing ring jumps back into an indentation position after an elastic deformation and a sliding of individual indentations, thereby triggering an operating noise.
Particularly preferably, the engagement section is formed to interact with the recess in the shaft in such a manner that a gap is formed between the engagement section and the recess in the radial direction to allow a deformation of the securing element in the radial direction.
In a further preferred embodiment, the engagement section together with the recess forms a spring-and-groove connection in the mounted state of the pawl nut such that the engagement section breaks off when the pawl nut is subjected to increased torque along the loosening direction. The engagement section thus advantageously forms a weakest link, whereby damage to the shaft can be prevented. At the same time, the indentation between the securing element and the pawl nut can be designed to be particularly resistant to rotation, as the pawl nut does not have to be loosened to release it.
Particularly in connection with the aforementioned gap between the engagement section and the recess, a spring-and-groove connection has the advantage that, compared to a pawl indentation, a force transmission continues to exist, in particular via a form-fit. In contrast, a gap between pawl indentations could lead to the risk of the indentation flanks of the pawl indentations damaging each other due to insufficient engagement and also sliding against each other along the loosening direction.
Further preferably, the pawl indentations of the pawl nut and/or the pawl indentations of the securing element have asymmetrical indentation flanks which are aligned in such a manner that first flat indentation flanks abut against each other along the tightening direction, in particular to ensure a one-directional sliding of the pawl nut and an elastic deformation of the securing element, and second steep indentation flanks abutting against each other along the loosening direction in order to interlock the pawl nut with the securing element in one direction.
In particular by the first flat indentation flanks abutting against each other in a tightening direction, the first flat indentation flanks slide against each other, in particular by the securing element becoming elastically deformable in the radial and/or circumferential direction. This results in a kind of ratchet-like movement, the pawl nut acting as a kind of ratchet in one direction along the tightening direction. Along the loosening direction, second indentation flanks which are relatively steep compared to the first indentation flanks are in contact with each other, in particular a transmitting force component acting essentially in the circumferential direction and a force component in the radial direction not being sufficient to deform the securing element. For this reason, the indentations interlock and thus secure the pawl nut against a loosening rotation.
In particular with a radial arrangement of the pawl indentation in conjunction with the above-mentioned asymmetrical indentation flanks, a radial force component on the first flat indentation flank in the tightening direction is greater than a radial force component on the second steep indentation flank in the loosening direction for the same torque. This favors elastic deformation of the securing element in the radial direction due to interaction between the first flat indentation flank and sliding of the first indentation flank along the tightening direction.
Particularly preferably, the first flat indentation flank has a radius of 4 mm to 6 mm, preferably 5 mm, and/or a flank height, in particular of a straight first flat indentation flank, of 0.8 mm to 1.2 mm, preferably 1 mm, in the radial direction and/or in that second steep indentation flank has a radius of 0.4 mm to 0.8 mm, preferably 0.5 mm to 0.75 mm. In particular, the relatively small radius of the second steep indentation flank results in a pawl indentation in the loosening direction, which has a locking effect essentially in the circumferential direction.
Preferably, the first flat indentation flank having the above-mentioned radius can be produced in a milling process. Alternatively or additionally, the first flat indentation flank can preferably also be formed in a straight line, in particular in a straight line within the specified flank height.
It is further preferred that the pawl indentation has indentations in 15° angle sections in the circumferential direction, preferably having a number of indentations between 22 and 26, particularly preferably 24. This number of indentations is particularly preferred for a securing element having an outer diameter of 29 mm to 31 mm. This fine tuning of the number of indentations in particular allows the topper element to be fastened without play or over-tightening along the screwing axis, especially in comparison to castle nuts having a split-pin lock.
Preferably, the pawl indentation in the pawl nut forms sections without indentations, in particular three sections evenly distributed along the circumference, which preferably reduce the total number of indentations by 35% to 40%. By forming sections without indentations, a sliding along the tightening direction can be favored and thus a torque for tightening can be reduced, in particular to enable manual screwing.
Preferably, the pawl nut mounts the securing element in an interior radial slot, the pawl nut having a frontal deforming section, which holds the securing element along the screwing axis in the deformed state, adjacent to the slot. In other words, this forming section forms a stop with the securing element along the screwing axis, so that the securing element is guided along the screwing axis for being screwed onto the shaft.
In a preferred embodiment, the pawl nut additionally mounts, preferably captively, a freely rotatable sliding disk along the screwing axis for abutting against the topper element, in particular in a form-fitted mounting, in order to reduce a friction coefficient between the pawl nut and the topper element in the mounted state. This means that the topper element can be braced on the shaft along the screwing axis without experiencing a force component in the circumferential direction.
In addition, the invention also relates to a shaft having at least one aforementioned pawl nut having a securing element, the at least one pawl nut being screwed onto at least one thread-shaft section of the shaft and the shaft forming at least one recess, in particular in the form a longitudinal groove, along the screwing axis, the securing element engaging into the recess with at least one engagement section, in particular into a spring-and-groove connection, in order to hold the at least one pawl nut on the shaft in the mounted state along a loosening direction and to brace a topper element on the shaft. For the purposes of the invention, a shaft can be understood in particular as a gear shaft or a drive shaft for a wheel bearing. In particular when using several topper elements and a shaft having several thread-shaft sections, several pawl nuts can be used and screwed onto the shaft in order to brace a topper element in each case. To reinforce the securing effect of the pawl nut, two recesses can preferably be disposed in the shaft, the securing element engaging accordingly in the shaft with two engagement sections.
In a preferred manufacturing method of one of the aforementioned embodiments of the pawl nut, a radial slot having an indentation contour is formed in a pawl nut blank along the screwing axis, in particular by means of a stamping process, above an inner thread. Preferably, a frontal deforming section is then formed further above the indentation contour along the screwing axis. Preferably, a centering section is formed along the screwing axis between the inner thread and the pawl indentation in order to center the pawl nut blank with respect to an embossing tool and to guide it along the screwing axis. Further preferably, the centering section has a larger inner diameter than the inner thread in order to form a stop to the inner diameter along the screwing axis.
Additionally or alternatively, the centering section can also form a defined distance between the inner thread and the pawl indentation in order to adapt the pawl nut to a predefined shaft geometry. For example, the recess can be formed at the end of the shaft and a topper element can be disposed at a distance from the recess along the screwing axis, a length of the centering section being formed in such a manner that the pawl nut having an inner thread can be screwed onto the shaft, the topper element can be braced and at the same time the securing element engages in the recess at the end of the shaft.
Preferably, the pawl nut is designed as a round body formed along the screwing axis, which has an attack or engagement outer contour for fastening tools, in particular hexagonal tools, in particular in the area of the inner thread. Preferably, the outer contour in the area of the pawl indentation and the centering section is cylindrical, in particular without a hexagonal geometry, in order to preferably be able to guide a stamping and/or deforming tool on the outer contour.
In a preferred assembly method for the pawl nut, the securing element is inserted into the radial slot within the pawl nut along the screwing axis and the pawl indentations in the pawl nut are brought into engagement with those of the securing element. To axially secure the securing element, the deforming section is deformed radially inwards in a next step, in particular flanged, to form an axial stop with the securing element.
The pawl nut having the securing element can then preferably be screwed onto the shaft, the engagement section of the securing element being brought into an engagement position with the recess in the shaft, in particular a longitudinal groove, by rotating the pawl nut and preferably engaging in a form-fitted manner in the circumferential direction. In particular, by further rotation of the pawl nut along the tightening direction, as already described above, the pawl nut can be screwed on to brace the topper element relative to the stationary securing element, the securing element acting as a self-locking device in a loosening direction for the pawl nut.
Further advantages and details of the invention can be yielded from the following description of preferred embodiments of the invention and from merely schematic drawings.
Identical elements or elements with the same function are marked with the same reference numbers in the figures.
In order to enable the one-directional rotatability, the pawl nut 10 is preferably in an operative connection with the securing element 18 by means of pawl indentations 20a, 20b, the securing element 18 preferably becoming elastically deformed when rotated in the tightening direction D1 and the pawl indentations 20a, 20b sliding against each other in a ratchet-like manner.
Along the screwing axis S, the slot 30 is preferably higher than the thickness t of the securing element 18 in order to form a guide section with limited translation possibility of the securing element 18 along the screwing axis S and a kind of bearing play in relation to the pawl nut 10. This translation possibility allows the engagement section 22 of the securing element 18 to align itself during an assembly step. As soon as a non-aligned engagement section 22 is in contact with a front 40 of the shaft 14 during assembly, the securing element 18 can move within the slot 30 along the screwing axis S until the engagement section 22 overlaps and engages in the recess 24 in the shaft 14 by further rotation of the pawl nut 10. Engagement of the engagement section 22 can be facilitated in particular if the securing element 18 forms a gap to the deforming section 32 at the start of assembly.
In
As
In particular,
According to
In
Preferably, first flat indentation flanks 21a, in particular of the pawl indentation 20a of the pawl nut 10, according to
Preferably, indentations are arranged in circumferential directions in 12° to 18°, in particular 15°, angle sections. Further preferably, several sections without indentations 36, in particular three, are disposed within the pawl indentation 20a of the pawl nut 10, which preferably reduces the total number of teeth by 35% to 40%. As a result, the engaged indentations can be reduced and a tightening torque can be reduced, and a deformation of the securing element 18 can be facilitated, in particular to enable manual assembly of the pawl nut 10.
The dimensions of the securing element 18, in particular the thickness t shown in
A combined view of
In a preferred manufacturing method, the pawl indentation 20a of the pawl nut 10 is embossed along the screwing axis S as shown in
The pawl groove 10 described so far can be modified or altered in a variety of manners without deviating from the idea of the invention. For example, it is conceivable that the pawl indentations 20a and 20b are also formed along the screwing axis S and act on each other. In this case, a one-directional loosening of the indentation 20 could be achieved by elastic deformation of individual indentation flanks 21, whereby play along the screwing axis S would then have to be prevented.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2021 105 659.2 | Oct 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/076324 | 9/22/2022 | WO |
