Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICE FOR TEMPORARY MECHP~ICA~J ATT~CHMENT OF AN
OBJECT TO A S~PPORT AND RAPID EJECTION OF THE OBJECT
F~OM THE SUPPORT
BACKGROUND OF THE INVENTION
Field of the invention
The invention concerns the temporary mechanical
attachment of an object to a support, the rapid
separation of the object from the support and its
ejection with a precisely oriented speed, in particular
to launch it without external guidance.
It finds an advantageous but by no means exclusive
application in separation/ejection operations on board
spacecraft such as satellites. It can also find
applications in various terrestrial vehicles, maritime
vehicles (surface vessels and submarines) and airborne
vehicles (aircraft of all kinds) in which a temporary
connection is made that is to be released subse~uently,
with immediate and precise movement of the object in
question (for example to launch it with no external
guidance).
A particular application of the invention is to
conducting scientific experiments in the upper atmosphere
or to exploring the planets of the solar system using an
automatic probe. For example, it can be used to eject a
storage vessel containing a chemical substance to be used
as a tracer to study winds or magnetic fields; a storage
vessel of this kind can be ejected from an artiEicial
platform such as a sounding rocket or an interplanatory
probe.
Description of the prior_art
Various mechanisms are already known for providing
temporary attachment of this kind followed by rapid
separation and more or less forcible ejection, for
achieving clean separation between the object and its
support.
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The following documents are particularly noteworthy
in this respect: US-4 554 905, W0-82/02527, U~-3 887 150,
US-2 ~88 294, US-3 196 745, US-3 597 919, US-4 002 120
and US-4 187 759, or the document EP-0 363 242 which
proposes a device for temporary fastening of two members
to each other and their subse~uent separation
characterized in that it comprises a male member coupled
to one of the members and a female member coupled to the
other member, said female member comprising in a hollow
body elongate along an axis X-X a retaining sleeve
adapted to reiract radially onto the male member or to
expand, a piston sliding axially to re~ract/expand said
retaining sleeve and, in the piston, disposed along the
axis X-X, an ejector finger which is coupled to it by a
lS fragile member, selective control means being provided
either to control only the movement of the piStOII or
additionally to break the fragile member and cause axial
sliding of the ejector finger projecting axially towards
the piston.
In practise these documents propose the use of
pressure type energy for release or separation. This
energy may be pneumatic, hydraulic or pyrotechnic, for
example, depending on the application. In the
particularly important case of pyrotechnic energy, the
pneumatic effects of combusting an explosive substance
are used.
Pyrotechnic energy is also used in separator
devices of the type: explosive bolts, explosive cutters
or pyrotechnic release systems which retract an abutment
member. They are usually associated with separator
pistons.
Taken as a whole, the various documents mentioned
above hardly concern themselves with the subsequent
movement of the object.
The document FR-2 616 852 is directed to a
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mechanism for commanding the separation of a member from
a support with which it is initially in contact. The
ejection speed and acceleration are perfectly controlled.
This document teaches how to apply an accurately defined
amount of energy to the object to be ejected to achieve
this result.
Finally, the document F~-2 550 756 discloses a
mechanism specifically designed to eject aircraft seats.
It has become clear that such mechanisms are
incapable in themselves of controlling accurately the
amplitude and the orientation of the ejection speed, in
particular because they do not allow for manufacturing
tolerances of the ejector mechanism components or the
tolerances for mounting the object to its support. This
is the case in the aforementioned document EP-0 363 ~42,
for example, which is primarily (but not exclusively)
directed to the simple releasing of various equipments
such as arms or panels of artificial vehicles.
The device disclosed in the document FR-2 616 852
provides a piston to eject the object by applying thrust
to its base. The ejection quality depends significantly
on the following parameters:
- the stiffness of the parts, in particular the ejector
piston and its guide members,
- the accuracy with which the guide parts are
manufactured and assembled,
- the position of the centre of mass re]ative to the
thrust axis, with which it may be coaxial, and a main
axis of inertia of the member or object to be ejected,
3~ especially if rotation about the main axis is to be
imparted to the object, as is the case with the present
invention,
- the quality of implementation of the abutting
relationship between the piston and the member to be
ejected.
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Similar remarks apply to the document EP-0 363 242.
It is found that the quality of ejection is
directly conditioned by the geometrical quality of the
ejector and the initial distribution of clearance.
The main consequences are: delicate adjustment,
inevitable and significant parameter spread and great
difficulty in modelling the ejector (to take into account
stiffness, clearance, impact, etc).
To overcome the aforementioned drawbacks, the
invention is directed to prvviding a simple and reliable
mechanism combining the three functions of attachment,
instantaneous release and ejection at a speed that is
controlled at least in terms of its orientation, in which
the effects of inevitable uncertainties in the
manufacture and the assembly of the parts of the
mechanism and of the object relative to the mechanism and
to the support are minimized, friction and unwanted
vibration also being minimi~ed, the three functions being
commanded by any appropriate known type energy source
(external to the mechanism provided by the invention)
adapted to provide an accurate amount of pressure energy.
The attachment function consists in assembling and
mechanically attaching the object to its support even
under severe environment conditions (particularly
vibration and in some instances the vacuum of space).
The relative positioning of the two parts must be highly
accurate and this must be achieved in combination with a
simple coupling ensuring reliability of operation and
implementation.
The result to be achieved for the release function
is instantaneous uncoupling of the two parts without
disturbing the ejection phase.
The fast ejector device must impart a given
acceleration to the object to be ejected by means of a
thrust ~orce generating, at the end of ejection proper
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~at the nominal values), only a given longitudinal
velocity VL~ notably because of accurate control of the
friction between the object and its support when thrust
is applied to the object.
SUMMARY OF THE INVENTION
The present invention consists in a device for
tempoxary attachment of an object to a support and
release and ejection of said object comprising a female
body adapted to be fixed to a support and a male member
coupled to the object and adapted to enter and leave the
~emale body along an axis, in said female b~dy beinq provided
retaining means with jaws adapted, according to
their axial position relative to a frustoconical guide
ramp tapering outwardly towards the object ~, to
retract radially onto a radially projecting annular
portion of the male member or to move away therefrom when
acted on by operating means comprising an operating ram
piston rod coaxial with the male member and ejector means
carried by said piston rod of said ram adapted to push
said male member of said objec~ along said axis towards
the exterior of said body, in which device:
- said frustoconical guide ramp is fastened to said
body,
- said ejector means are fastened to said piston
rod of said operating ram and comprise a transverse
bearing surface which bears during the holding phase
against a transverse bearing surface of said male member,
- said retaining means comprise a bush mobile
axially within said body and comprising an annular
transverse flange disposed between two transverse steps
on said piston rod and a plurality of radially flexible
blades e~ui-angularly distributed about said axis
fastened to the perimeter of said flange, extending
towards said male member and whose free ends carry said
jaws, said bush further comprising spring means urging
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said jaws radially outwards.
It will be understood that an important feature of
the invention is the use of a tulip-shape b~sh whose
petals (the blades ending in the jaws) have a clamping
and centering function during the holding ~hase, with the
particular -feature that this bush accompanies the object
in its initial movement (so that transverse disturbances
are minimized) during ejection before its holding action
is released automatically.
The invention is distinguished from the document
EP-0 363 242 in particular by virtue of its limited
number of moving parts (the large number of parts
disclosed in this prior art document results in
particular from the objective o that document which was
to enable automatic execution prior to ejection of a
large number of locking and unlocking cycles, which is
not a requirement in the present instance because manual
operation is possible), and by the fact that the
retaining means, which are in a plurality of separate
parts, have virtually no movement other than the radial
movement resulting from retraction of ~he case around
said bush~
According to optionally combinable preferred
features of the invention:
- said bush is mounted to slide between said steps,
a compression spring being disposed axially between said
flange and said step which is nearer said male member,
- said step which is nearer the bottom of said
female body is adjustable in position in the axial
direction,
- said step is at least part of a nut screwed onto
a screwthreaded portion of said piston rod of said ram,
- said frustoconical guide ramp is a chamfer
flanking the mouth of said female body,
- said bush is adapted to move axially between an
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open configuration in wh.ich said jaws are outside said
female body and a closed configuration in which said jaws
bear on said ramp through their radially exterior
surfaces,
S - said male member comprises a frustoconical wall
tapering outwardly towards the interior of said female
body and said jaws have interior and exterior
frustoconical surfaces whose cone angles relative to said
blades are substantially equal to the cone angles of said
frustoconical wall of said male member and of said guide
ramp, respectively, the cone an~le of said exterior
surfaces being greater than that of said interior
surfaces,
- said spring means urging said jaws radially
outwards are said flexible blades themselves,
- said spring means urging said jaws radially
outwards are leaf springs extending along said flexible
blades,
- said ejector means comprise a transverse bearing
surface a~ the end of said piston rod of said ram,
- said transverse bearing surface comprises a
centering nipple projecting from a plane surface adapted
to enter a blind hole in said male member,
- said ejector means and said step which is nearer
said male member are formed on a member attached to said
piston rod of said ram,
- said piston rod of said ram is coupled to said
female body by a fragile pin,
- sai.d step which is nearer the bottom of said
female member is adjustable in position in the axial
direction and at least one access window is provided in
said female body.
Objects, features and advantages of the invention
will emerge from the following description given by way
of non-limiting example with reference to the appended
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drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a partially cut away diagrammatic
perspective view of a system in accordance with the
invention for mechanical attachment of an object to a
support.
figure 2 is a detail view in axial cross-section of
a system as shown in figure 1.
Figure 3 is a perspective view of the tulip-shape
bush shown separately.
Figure 4 is a detail view showing one embodiment of
each petal of the bush.
Figure 5 is a view similar to figure 2 showing the
locking phase of a male portion of the object.
Figure 6 is a similar view showing the ejection
phase.
Figure 7 is a variation on figure 2.
DETAILED DESCRIPTION OF THE INVENTION
Referring to figures 1 and 2, a temporary
attachment system 1 in accordance with the invention
comprises a male member 2 shown in dashed outline in
figure 1 adapted to be fixed to an object 3 only part of
which is shown only in figures 2, 5, 6 and 7 and a body 4
comprising a housing 5 which the male member can enter in
2~ a reference direction X-X and which is adapted to be
fixed by any appropriate known means to a support 6.
A ram 7 is disposed in this housing with its body
7A fastened to the body 4 and its piston rod 7B coaxial
with the direction X-X and with the male member 2. At
its free end the rod 7B has a transverse bearing surface
8 adapted to bear axially against a transverse bearing
surface 9 of complem~ntary shape at the base of the male
member.
In this example the part 8 is a plane surface from
which projects a centering nipple 10 coaxial with the
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rod. The bearing surface 9 is a plane surface at the
center o~ which is a blind hole 11 adapted to receive the
centering nipple.
The bearing surface 9 of the male member 2 is
joined to the remainder of the object 3 by a
frustoconical wall 9A tapering inwardly towards the
interior of the object so that the male member comprises,
along the bearing surface, a radially projecting annular
ring.
The piston rod of the ram comprises two steps 12
and 13 facing each other in the axial direction.
The transverse flange 14 slides on the piston rod
between these steps. It is joined at its perimeter to
radially flexible blades 15 extending axially towards the
object and the ends 16 of which are widened in the radial
direction to form jaws having interior and exterior
frustoconical bearing surfaces 17 and 18 inclined
relative to the axis and converging towards the interior
of the support.
The interior frustoconical bearing surfaces 17 are
adapted to be applied to the frustoconical wall 9A of the
male member. The exterior frustoconical bearing surfaces
18 are adapted to be applied to a frustoconical chamfer
19 bordering the mouth of the housing 5 in the body 4.
A spring 20 (not shown in figure 1) is compressed
axially between the step 13 and the flange 14 so as to
urge the latter elastically towards the step 12 and
therefore away from the object. The step 12 is
advantageously adjustable in the axial direction, being
shown in figure 2 as a nut 21 in contact with a locknut
22 on a screwthreaded portion 23 of the piston rod.
Figure 2 shows a radia~ fragile pin 25 to hold the
piston rod in position relative to the body 4.
The flange 14 and the blades 15 are parts of one
and the same part constituting a bush surrounding the
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piston rod 7B. This bush is in the shape of a tulip with
the blades 15 constituting its petals (three in this
example *~ui-angularly spaced around the axis at 120).
To facilitate fitting the tulip the piston rod 7B
is in two parts, namely the piston rod proper of the ram
and a sleeve 27 screwed onto this.
Windows 29 are advantageously provided in the body
4, in particular to enable access to the nuts 21 and 22.
Figures 3 and 4 show the tulip 26 in more detail.
The benefit of its unitary construction is accurate
positioning of the frustoconical surfaces 17 and 18,
which is necessary for proper centering of the male
member and for proper distribution of clamping forces
between the three branches 15.
The cone angles al and a2 are preferably such thato
(1) a2 is greater than the angle of friction between
the body and the tulip,
(2) ~l is greater than the angle of friction between
the object and the tulip,
(3) a2 is greater than al.
Conditions (1) and (2) prevent the risk of jamming
of the device and condition (3) assures priority in time
of release of the tulip from the body over release of the
tulip from the male member.
The angles al and a2 are respectively the cone
angles of the frustoconical surfaces 17 and 18 relative
to the longitudinal axis of the associated blade 15.
As can be seen from the representation of the
holding configuration in figure 2, because the e~terior
surfaces 18 of the jaws 16 bear on the chamfer l9 and the
interior surfaces 17 bear on the frustoconical wall of
the male member the compression force T applied by the
spring towards the bottom of the housing 5 has a wedging
effect which generates on the jaws forces R directed
towards the axis which because of the cone angle al apply
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to the male member forces P directed towards the axis and
downwardly, so effectively clamping the male member
against the bearing surface 8.
It will be understood that in figure 2 the cone
angle a2 of the exterior surfaces i.s such that the
wedging effect of the ramp 19 enables correct retention
by virtue of the spring 20 whilst leaving a clearance e
between the flange and the interior bearing surface 12. --
The flexible blades 15 are urged elastically
radially ou~wards either by their inherent elasticity
(figure 2) or by additional leaf springs 30 (figure 4) or
31 (figure 7).
In the case of figure 4, for example, the tulip is
machined in its closed position (the nominal clamping
position) and the leaf springs 30 open it (force F)
during fitting and during ejection.
The dimensions 11 and 12 are determined by
conventional bending calculation formulae on the basis of
the characteristics of the materials employed and of the
required equilibrium configuration (~-open tulip").
In the open position, the force F provided by the
spring in this position balances the resisting force of
the premachined petals (bending force). There is
therefore equilibrium between blades 15 and leaf springs
30 operating in bending.
The procedure for mounting the payload, which
changes the configuration from the mounting configuration
to the holding configuration (figure 5), is as follows:
(a) the tulip 28 is in the open configuration (nut 21
screwed fully upwards and compressing the spring 20),
(b) the object is offered up to the positioning
interface 8 + 10,
(c) the nut 21 is unscrewed (the tulip moves down and
the petals clamp the object),
(d) the position of the nut 21 is adjusted to obtain a
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clearance _ of 0.5 ~ 0.1 mm between the nut ~1 and the
tulip,
(e) the locknut 22 is locked against the nut 21.
Positioning and holding are obtained:
- by the centering nipple 10 and the plane bearing
surface 8 joined directly to the pyrotechnic ram 7; this
provides a longitudinal abutmen~ and a point on ~he axis
of the object (payload);
- by the tulip which provides additional centering and
~0 clamping with axial and radial components; clamping is
achieved by the wedging effect of the frustoconical
bearing surfaces (see above), the necessary clamping
force being supplied by the compression spring; the
benefit of this spring as compared with any other
tensioning system (screw/nut, for example) is the control
it provides over the modulus of the clamping force when
~- mounting the object and thereafter in time, compensating
relaxation.
A screw/nut system exerts clamping torques which
generate tension forces subject to considerable spread;
; the pre-tensioning effect thus generated is not
accurately controlled because of this. With a spring, a
specific force is generated and when contact mating
occurs during mounting or thereafter in time, the spring
is able to compensate for play to provide a stable force.
It will be understood that in this example the axial
symmetry object is not positioned in rotation. Such
positloning could be provided by a second nipple on the
plane bearing surface, for example.
The mobile assembly is held in position relative to
the body by the shear pin 25.
Figure 6 shows the ejection phase.
The plane bearing surface 3 between the object and
the ejector constitutes the movement imparting interface.
When the ram is deployed the retaining pin breaks and the
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mobile assembly (ram + tulip) applies thrust to the
object. During this movement the tulip is rapidly
disengaged from the points at which it bears on the body
and as a result of this the tulip opens. The object is
released and enters a ballistic phase when the thrust is
removed.
To facilitate assembly the body 4 is advantageously
a cylindrical part attached by means of a screwthreaded
ring to a housing for the body and the chamber of the
ram.
To impart an initial rotation to the body about its
axis provision may be made for rotational coupling
between the ram and the object and helical guidance of
the ram 7.
It goes without saying that the foregoing
description has been given by way of non-limiting example
only and that numerous variations thereon may be put
forward by the man skilled in the art without departing
from the scope of the invention.
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