Fastening element

A fastening element with a dowel-like bushing which can be fixed in a bore is described. In the axial bore of the bushing there is a retaining pin that can be urged into the bore. The pin can fix a member that is to be fastened between its broadened head having a slot, or a cross-recess and the bushing. The shank of the retaining pin is provided with at least one transversely extending groove into which, in the pressed-in state of the retaining pin, a spring-loaded snap-in locking element engages and is guided in a cross-slidable manner in the bushing and is forced back into its released position by turning the retaining pin.

The invention refers to a fastening element with a dowel-like bushing which 
can be fixed in a bore, for instance in a bore of a piece of furniture, 
wherein in the axial bore of the bushing a retaining pin is supported 
which can be urged thereinto and which can fix a member to be fastened, 
preferably a fitting, between its broadened head having a slot or a 
cross-recess and the bushing. 
There are known various types of such fastening elements which can quickly 
and easily be mounted by hand or by using only simple tools. Therein the 
retaining pin is anchored in the dowel bushing either in a force-locking 
manner and/or in a form-locking manner. In known fastening elements in 
which the dowel bushing is held in its bore in a force-locking manner, 
either a large force for urging apart the bushing is required or only a 
low stability of the connection can be achieved. In known fastening 
elements in which the retaining pin is additionally anchored in the dowel 
bushing in a form-locking manner, close manufacturing tolerances must be 
observed for often complex types of fastening elements. 
Therefore it is an object of the present invention to provide a fastening 
element of the kind indicated above which has a compact construction and 
permits an easy, secure and quick mounting and can also be released again 
in a simple and quick manner without requiring any special tools. 
According to the invention said object is solved for a fastening element of 
the generic type in that the shank of the retaining pin is provided with 
at least one substantially transversely extending groove into which, in 
the pressed-in state of the retaining pin, a spring-loaded snap-in locking 
element engages which is guided in a cross-slidable manner in the bushing 
and which is forced back into its released position by turning the 
retaining pin. 
Hence, the fastening element according to the invention can be mounted 
easily and quickly due to the fact that the retaining pin is pressed into 
the axial hole of the dowel bushing in a position in which its transverse 
groove faces the snap-in locking element, until the snap-in locking 
element engages the transverse groove. By a simple turning of the 
retaining pin by means of a screwdriver through approximately 80.degree., 
the snap-in locking element can be pressed out of the lock-in groove so 
that the retaining pin can be pulled out of the bore of the dowel bushing 
for releasing the connection. 
Advantageously, the snap-in locking element consists of a transverse pin 
guided in a slot-like, substantially radial guideway of the dowel bushing. 
Advantageously, the guideway intersects a blind hole being open towards 
the bore, in which a compression spring is held which, on the one hand, 
rests on the bottom of the blind hole and, on the other hand, on the 
transverse pin. 
Advantageously, the guideway inclines from the section of the center axis 
of the bore of the dowel bushing towards the end of the bushing. 
In a further aspect of the invention the base of the transverse groove of 
the retaining pin is curved in an inclined manner in its direction of 
rotation for opening. Through said curvature the transverse pin is urged 
back out of the transverse groove with increasing lever arm so that the 
release of the connection can be obtained with a reduced expenditure of 
force. 
Advantageously, the transverse groove extends in a spiral-shaped and 
inclined manner towards its end with the curved base. By said design of 
the transverse groove the retaining pin is slightly lifted out of the bore 
during the turning thereof into its opening position so that in its 
released position it can more easily be pulled out of the bore of the 
dowel bushing. 
In a further aspect of the invention the axial bore extends eccentrically 
to the center axis of the dowel bushing, the shank of the retaining pin is 
correspondingly arranged eccentrically at the head formed as a flush head, 
and the fastening bore of the member to be fastened is provided with a 
reduced edge formed complementary to the truncated lower part of the flush 
head. Therein the eccentricities of the shank to the head and the bore of 
the dowel bushing are coordinated with each other such that the head can 
only be pressed into the reduced edge of the fastening bore when the 
retaining pin is in a position in which the transverse pin can come into 
engagement with the transverse groove. When now the head is turned for the 
purpose of releasing, the head is not locked-up in the cavity formed by 
the reduced edge of the fastening bore, as the truncated bevellings of the 
head and of the reduced edge are coordinated with the oblique course of 
the transverse groove of the retaining pin so that during turning the pin 
out of the lock, the truncated jacket of the head substantially rolls off 
on the complementary formed edge. Advantageously the dowel bushing being 
separated in an axial center plane consists of two mirror-inverted parts 
connected by a tenon-bore joint. The two parts are preferably made of 
injection moulded parts made of plastic material so that the desired 
contours including the outer serrated profile can be formed in an exact 
manner. 
The transverse groove of the retaining pin is preferably narrowed towards 
its base so that given manufacturing tolerances are compensated and the 
retaining pin is held in its locked position free from backlash. The 
narrowing can be effected in that the side flanks of the groove converge 
towards the base thereof, the groove being broader in its opening section 
and narrower in its base than the diameter of the snap-in pin. 
According to a second embodiment of the snap-in connection according to the 
invention the snap-in pin is held rotatably but undisplaceably in axial 
direction in a jacket partially surrounding it which is provided with a 
cutout uncovering the transverse groove of the snap-in pin and with a stop 
by means of which it is held stationary at a counterstop of the bore of 
the dowel bushing. In this development it is ensured by means of the stop 
and the counterstop that only in the correct turning position the snap-in 
pin can be pressed into the bore of the dowel bushing for its engagement 
with the snap-in locking element or the transverse pin so that the bore of 
the dowel bushing can also be arranged in the axis thereof. 
Advantageously the stop is formed by a cut in the jacket following the 
cutout, extending freely downwards and being carried out in a plane 
parallel to the pin axis. 
The counterstop may consist of a chord-like step arranged in the bore of 
the dowel bushing. 
Advantageously a resilient leg bent off a ring held in a ring groove of the 
bore of the dowel bushing acts upon the transverse pin. 
The jacket can be connected with the retaining pin in a rotatable but 
axially stationary manner in that it is provided with an annular bead at 
the inside of its through-hole which engages a ring groove of the 
retaining pin. 
In a further aspect of the invention the head of the pin is provided with a 
radial extension the lateral step-like edges of which form stops for a 
counterstop of the jacket. Therein the stops and counterstops are 
coordinated with each other such that depending on the interacting stops 
the pin is either in a position in which it can come into a locking 
engagement with the snap-in locking element in the dowel bore or in its 
released (unlocked) position. 
According to a third embodiment of the invention the shank of the retaining 
pin is provided with a ring groove into which in the pressed-in state of 
the retaining pin at least one spring-biased snap-in locking element snaps 
in which is guided in the dowel bushing so that it is substantially 
displaceable in transverse direction, the shank of the retaining pin is 
provided with a thread above the ring groove and together therewith is 
screwed into a bushing provided with a female thread and being held 
stationary with respect to the edge of the bore of the member to be 
fastened. Also in this fastening element according to the invention the 
snap-in pin can be locked in the dowel bushing by simply pressing it 
thereinto. The snap-in pin is already premounted at the member to be 
fastened, since the edge of the fastening bore is located between the head 
of the retaining pin and the threaded bushing screwed thereonto. For 
releasing the snap-in connection the pin is unscrewed from the threaded 
bushing so that the retaining pin with its ring groove is removed from the 
snap-in locking element. 
Advantageously, the dowel bushing is provided with two guideways extending 
obliquely outwards towards the end of the bushing, wherein the dowel bore 
consists of a blind hole and a compression spring is clamped in between 
the base of the blind hole and the two transverse pins. 
The threaded bushing may be provided with a reduced upper collar which 
rests upon a respective annular step of the dowel bore during releasing or 
unscrewing the retaining pin from the threaded bushing. 
The threaded bushing may be held stationary with respect to the member to 
be fastened in that at its upper end it is provided with at least one 
projection which engages a respective edge recess of the fastening bore of 
the member to be fastened.

The fastening element shown in FIG. 1 through 8 consists of a dowel bushing 
3 inserted into a bore 1 of a piece of furniture 2 or the like, said dowel 
bushing 3 being composed of two mirror-inverted halves 4, 5. The halves 4, 
5 of the dowel bushing dividing the dowel bushing 3 in a longitudinal 
center plane consist of injection moulded parts made of plastic material. 
Each half is provided with two tenons (pins) 6 and two bores 7 which are 
used for assemblying and holding together of the dowel bushing, when the 
transverse pin 9 has been inserted in the slot guideway 8 and the 
compression spring 12 has been inserted in the radial blind hole 10 
extending into the dowel bore 11, said pressure spring 12 being supported 
with its one end on the base of the blind hole 10 and with its other end 
on the transverse pin 9. The axial dowel bore is arranged eccentrically to 
the dowel axis. In order to ensure a good anchorage in the bore 1, the 
dowel bushing 3 is provided with a serrated profile 13 on its outer 
circumference. 
The retaining pin 14 consists of a cylindrical shank portion 15 carrying a 
head 17 provided with a cross-recession 16. The head 17 has a truncated 
sunk part 18 between an upper disk-like portion. At the lower smaller 
circular area of the truncated part 18, the shank 15 is added in 
accordance with the eccentricity of the dowel bore 11. The shank 15 has a 
cone-like tip 19 and above thereof a transverse groove 20 which extends in 
an oblique or spiral manner towards the tip 19. Towards its end the base 
21 of the groove is inclined slightly downwards, as can be seen in FIG. 
18. 
The member 22 to be fastened is provided with a fastening bore 23 having an 
inward flange, wherein the bore edge 24 is bevelled like a channel so that 
it matches with the truncated flush head 17, 18. The dowel bushing 3 is 
provided with a flat and circular recess 25 at its upper end which is used 
for centering the lower edge of the flanged fastening bore. 
For locking the fastening element, the retaining pin 14 is pressed through 
the fastening bore 23 into the dowel bore 11 in the direction of arrow A, 
so that the transverse pin 9 engages the transverse groove 20 in a 
snap-like manner in the locking position as illustrated in FIG. 2. Due to 
the eccentricity of the dowel bore 11 and of the shank 15 relative to the 
retaining pin 14, during insertion of the retaining pin the transverse 
groove 20 thereof is located on the side facing the transverse pin 9. 
For opening the fastening element the locking pin 14 must be turned with a 
screw driver in counterclockwise direction so that the retaining pin is 
screwed out of the dowel bore 11 due to the spiral design of the groove 
20, wherein the head of the retaining pin 15 is not blocked in the recess 
of the fastening bore, since the jacket of the truncated portion 18 of the 
flush head rolls off from the wall of the edge of the fastening bore and 
simultaneously comes out of the dowel bore in the direction of arrow B. 
When the transverse pin is located on the cylindrical jacket of shank 15 
of the locking pin 14, it can be pulled out from its position as shown in 
FIG. 3 in the direction of arrow B. 
The second embodiment of the fastening element which is shown in FIG. 10 
through 17 differs from the first one substantially only in that the 
snap-in pin 30 is arranged rotatably but stationary in an axial direction 
within a jacket 31 partially enclosing it. Jacket 31 consists of a 
tube-like part the inner contours of which are substantially adapted to 
the outer contours of the retaining pin 30. The retaining pin 30 is 
provided with a transverse groove 32 the side flanks of which are narrowed 
towards the rounded base thereof. Said transverse groove extends 
diagonally to the center axis of retaining pin 30. In the section of the 
transverse groove 32 the jacket 31 is provided with a cutout 33 uncovering 
it. In a plane extending in parallel to the plane of the transverse center 
line of the cutout 33, the jacket 31 is provided with a cut (free cut) 
extending from the lower end of the jacket in the manner as shown in FIG. 
13 into the cutout 33 so that two lower legs 34, 35 are formed the fronts 
36, 37 of which form stop surfaces. The jacket 13 is provided with an 
inwardly projecting bead 38 at its lower section in the manner illustrated 
in FIG. 11, said bead 38 engaging a ring groove 39 of the retaining pin 30 
such that the retaining pin 30 is connected with the jacket 31 so that it 
is rotatable but stationary in axial direction. 
The flush head 40 of the retaining pin 30 which is provided with a 
truncated section has a sector-shaped radial extension 41. Said extension 
41 has step-like stop areas 42, 43 on its two sides. On its annular front 
44, the head portion of the jacket is provided with an axial extension 45 
in the manner as shown in FIG. 13 which extends along the circumferential 
section as to be seen in FIG. 13. Also said extension has two step-like 
stop areas 46, 47 cooperating with the stop surfaces 42, 43 of the 
retaining pin. When the stop surfaces of one side contact each other, the 
retaining pin 30 is in its locking position as shown in FIG. 10, while the 
retaining pin is in its opening position illustrated in FIG. 11, when the 
two other stop surfaces abut each other. 
On its side at which the oblong hole 52 receiving the transverse pin 51 is 
located, the dowel bushing 50 is provided with a chord-like recess 53 
extending from step 54 above the oblong hole 52 towards the lower end of 
the dowel bore. Said recess 53 forming a plane stop surface constitutes 
the counterstops for the stop surfaces 36, 37 of jacket 31 formed by the 
free cut. 
Due to the recess 53 cooperating with stop surfaces 36, 37, the angular 
position of jacket 31 in the dowel bore in which the retaining pin can 
come into engagement with the transverse pin 51 is fixed. The locking and 
releasing positions of retaining pin 30 in jacket 31 are determined by 
stops 42, 43 and 46, 47. 
The transverse pin 51 situated in the slant guideway 52 is resiliently 
acted upon (pressed) by leg 57 bent off the retaining ring 58 in the 
manner to be seen in FIG. 18. Retaining ring 58 is held in a ring groove 
59 of the dowel bushing 50. 
The arrangement of said ring groove 59, of the slant guideway 52 and of the 
free cut 60 for the movement of the resilient leg 57 in the dowel bushing 
is illustrated best by means of the latter's mirror-inverted halves as 
shown in FIGS. 14 and 15. 
For mounting the fastening element in the manner as shown in FIG. 9, the 
retaining pin enclosed by the jacket 31 is pressed through the fastening 
bore 64 of the member 63 to be fastened into the dowel bore of the dowel 
bushing in a position in which the transverse groove 32 is located in the 
cutout 33 of jacket 31. As the jacket 31 can only be pressed into the 
dowel bore in an angular position relative thereto in which the stop areas 
36, 37 slide along the recess 53, it is guaranteed that the snap-in pin 51 
falls into the snap-in groove in a locking manner during the pressing-in 
process. The snapped-in position is shown in FIG. 10. 
For releasing the snap-in connection, the snap-in pin 30 is turned about 
180.degree. by a screwdriver for recessed-head screws into the position as 
shown in FIG. 11 in which the respective stops 42, 46 fix the position of 
the snap-in pin 30 in the jacket 31 so that the snap-in pin together with 
its jacket 31 can be removed from the dowel bore in the direction of arrow 
C in FIG. 11. 
In the embodiment of the fastening element according to FIG. 19 through 24, 
the snap-in pin 70 is provided with a shank below its flush head 71 being 
provided with a truncated section, said shank having an upper portion 
being provided with a thread 73, a portion following thereto and being 
provided with a ring groove 74, and a cone-shaped tip 75. The shank 
portion being provided with thread 73 is screwed into a threaded bushing 
76 consisting of a lower cylindrical portion 77 and an upper angular 
collar-like or flange-like broadening 78 having two radial projections 80, 
81 being offset by 180.degree. on its front side 79, the inner sides of 
which are inclined in accordance with the truncated part 72 of the flush 
head 71. The member 83 to be fastened is provided with a fastening bore 84 
the rim 85 of which is reduced corresponding to the truncated section 72 
of head 71 and is provided with two cutouts 86 being opposite to each 
other into which the projections 80, 81 engage in the manner to be 
inferred from FIG. 19. 
For premounting the fastening device, the threaded shank portion 73 of the 
retaining pin 70 is screwed into the threaded bushing 76 by intermediate 
positioning of member 83 to be fastened so that the member 83 to be 
fastened is fixed between head 71 and threaded bushing 76. 
Dowel bushing 90 is provided with a central blind bore consisting of a 
lower longer portion 91 with a smaller diameter and an upper shorter 
portion 92 with a larger diameter so that an annular step 93 is formed 
between said two portions. The dowel bushing is provided with two mutually 
opposite, obliquely extending oblong holes 94, 95 in which retaining pin 
96 is guided. The oblong holes 94, 95 extend towards the end of the dowel 
bushing 90 obliquely outwards. Between the base of the blind hole 91 
forming the dowel bore and the two retaining pins 96 a compression spring 
97 is clamped in the manner as illustrated in FIG. 19 which loads the two 
retaining pins 96 in the direction towards their position in which they 
are pushed towards each other. 
The retaining pin 70 premounted at the member 83 to be fastened in the 
manner as shown in FIG. 19 is pressed into the dowel bore in the direction 
of arrow D for mounting the fastening element, until the two retaining 
pins 96 engage in a snapping manner in the ring groove 74. The locked 
position is shown in FIG. 20. 
For releasing the snap-in connection the retaining pin 70 is turned by 
means of a screwdriver for recessed-head screws in the manner to be 
inferred from FIG. 21 in the counterclockwise direction so that the 
threaded bushing moves downwards from the locked position as shown in FIG. 
20 towards the base of the bore of dowel bushing 90 into the position as 
shown in FIG. 21 and thereby pushes the two retaining pins 96 by means of 
its lower annular front into their opening position in the end section of 
the two oblong holes 94, 95. In the position as shown in FIG. 21 the 
release position is substantially reached in which the member 83 to be 
fastened can be removed together with retaining pin 70 and the threaded 
bore 76 in the direction of arrow E.