Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to apparatus for the automatic adjustment
of the actual frequency of mechanical resonators of a magnetic material,
which are provided with pin-like holding elements, the adjustment bringing
the resonator frequency to a given theoretical frequency by the removal of
resonator material using a sand-blasting controlled in dependence upon a
difference frequency obtained from a comparison of the theoretical and
actual frequencies.
On account of their high oscillatory quality and their small
space requirement, mechanical resonators enjoy wide-spread use, for example
as frequency standards or in mechanical filters. In virtually all cases
of use it is of importance that the resonance frequency of such a mechanical
resonator should occur at a predetermined frequency that is set as accurately
as possible. As a result of the unavoidable requirement to allow production
tolerances in the production of the resonators, generally this requirement
is not sufficiently fulfilled, so that it is necessary to adjust the final
resonance frequency of such a resonator following its production. It is
known to carry out this process which is known as "adjustment~' or "balancing"
by removing resonator material with the aid of a grinding process, or b~
sand-blasting, or by the use of laser beams. In this connection a process
for the frequency adjustment of mechanical resonators is described in the
German Patent Specification No. 1,929,994 of Siemens AG, issued
October 21, 1971, in which the setting of the given resonance frequency
takes place by a controlled displacement of resonator material using sand_
blasting. In the process described in this patent, the resonators are
excited to mechanical oscillations which are converted into electric oscilla-
tions corresponding to the actual frequency of the resonators, and then
amplified. The amplified electric oscillations are subjected to comparison
with a theoretical value, and the bombardment of resonator material by
means of sand-blasting is controlled by the resultant difference frequencyO
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In order to achieve uniformly good results with this process however, it is
necessary to use uniformly bias-magneti~ed resonators, as these are excited
via a drive magnet to oscillations whose frequency is to be measured.
Therefore it is necessary for the resonators, having been pre-adjusted by a
grinding process, to be de-magneti3ed prior to the actual magneti~ation.
Following the actual adjustment process, 1the resonators must be
checked to establish whether their resonance frequency lies within the given
tolerance - frequency range, and if this is not so, i.e. when a particular
resonator is not capable of oscillation as required, that particular reson-
1~ ator must be selectively rejected.
Thus both prior to and following the actual adjustment process,additional operating sequences are required, with special associated devices.
This inevitably gives rise to long transport times between the individual
operating sequences and conveyance times for the individual devices, and
likewise increased outlay in personnel for the operation, and in the convey-
ance and servicing of these devices. Because of the different natures of
the individual operating sequences, and the associated devices, it is
difficult to fully automate such an adjustment process.
One object of the present invention is to provide an apparatus
for the frequency adjustment of mechanical resonators, in which all the
above-described operating sequences may take place fully automatically in
one relatively economical device.
The resonators which are to be adjusted are automatically conveyed
to the consecutive processing stations and can remain in the guide rail or
the holders of the rotary indexing table whilst thereon during all the
processing~ This obviates the need for manpower for the conveyance and
transportation of the resonators between individual processing devices.
Another advantage consists in the fact that a separate measurement
of the resonance frequency, which is normally required for conventional
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sorting of the resonators following the adjustment process, is rendered
unnecessary as the respective measurement which concludes the sand-blasting
adjustment for any resonator is stored and used to selectively control the
individual ejection stations for routing that resonator.
The combination of the various operating sequences required for
the adjustment of the resonators within one single device produces the
particularly advantageous possibility of a simple, central control of these
operating sequences.
Thus, in accordance with the invention, there is provided apparatus
for the automatic adjustment of the actual frequency of mechanical resonators
of magnetic material and provided with pin-shaped holding elements~ to adjust
their resonance to a predetermined theoretical frequency by the controlled
removal of resonator material using sand-blasting in aependence upon a
diffeIence frequency produced by comparison of the theoretical and actual
measured frequency, said resonators being conducted via a guide rail to be
demagnetized, and then abut against an end stop where each resonator actuates
a switch that serves to trigger a control signal and instigate the convey-
ance of that abutting resonator to a rotary indexing table provided with a
plurality of holders, that holder located opposite the end stop gripping
that resonator abutting against the end stop by its pin-like holding elements,
and raising above the end stop, the resonators thus accommodated in the
holders then being conveyed in sequence to individual processing stations by
a step-by-step rotation of the rotary indexing table, a drive control ~mit
for the rotary indexing table being fed with a control command from the sand-
blasting adjusting device at the end of each frequency processing step, which
command subsequently causes the rotary indexing table to execute a transport
step in which that resonator last received by a holder is conducted to a
magnetization station where it is magnetized, the following processing
station being that in which the sand-blasting adjustment is carried out, and
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comparator means being provided to store that measurement of the resonance
frequency which concludes any sand-blasting adjustment, said stored
resonance fre~uency then being compared with a given tolerance-frequency
range, and ejector means responding if its resonance frequency lies ou~side
the given tolerance-frequency range to cause that resonator to be ejected
in the next station, or if its resonance frequency lies within the tolerance-
frequency range, cause that resonator to be ejected in a next but one
station.
The invention will now be described with reference to the drawings,
in which:-
Figure 1 schematically illustrates a plan view of an entire sand-
blasting adjustment apparatus constructed in accordance with the invention;
Figure 2 is a side view of a holder on the rotary indexing turn-
table that is used in the Figure 1 embodiment;
Figure 3 is a plan view of the holder shown in Figure 2;
Figure 4 is a longitudinal section through the holder;
Figure 5 is a section through the guide rail of the embodiment
shown in Figure 1 in the region of an end stop with mutually opposed open
clamping jaws of a holder partly illustrated;
Figure 6 shows a section, positioned as in Figure 5 with the clamp-
ing jaws closed and with the relevant resonator in its clamped position;
Figure 7 illustrates a section through an open magnetization
station;
Figure 8 is a section through the magnetization station of
Figure 7 when in the clamping position;
Figure 9 illustrates a first ejection station; and
Figure 10 illustrates a second ejection station.
The adjusting device shown in Figure 1 consists of a plurality of
ass-emblies which are mounted on a common base plate 1. Arranged in the
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centre, for the transport of resonators to an actual adjustment station 3
is a pneumatic rotary indexing turn-table 2 of the type commercially avail-
able under the reference ST-270 from the Vesto company, this being provided
with twelve indexing positions. For the support of the resonators, the
rotary indexing table possesses a number of holders 3, which in number
conform to the number of indexing positions, and wh-ich`are arranged con-
centrically to its axis or rotation and at equal in~tervals. The resonators
are conveyed to the rotary indexing ~able by means of a feed device which
is secured to the base plate and which contains a vibrator device 4 and a
guide rail 5 which is connected to the output of the vibrator device to
receive and feed the resonators along. In the represented exemplar~ embodi-
ment, the vibrator device 4 is a conveying and sorting device commercially
available under the name "Sortimat", which is set up for the resonators
which are to be adjusted, and comprises a vibrator base with an electromag-
netic vibrator, a sorting trough and a separately arranged indexing device 6
via which the feed speed of the resonators can be controlled.
The resonators, emerging in a row from the vibrator device 5, are
conducted to the guide rail 5, which is initially horizontal and then slants
downwards, and on passing along said guide rail they first pass through a
photo-electric station 7, which is in the form of a light barrier having a
light source and opto~electric detector monitoring station, which serve to
monitor the continuous transport of the resonators and control the switching
on and off of the vibrator device, then pass through a demagnetization
station 8 in the form of a coil, and subsequently abut against an end stop 9
that is provided in the form of a lever on the guide rail~ The pressure
which thus occurs actuates a micro-switch (not shown) as a result of which
the correct positioning of each resonator against the end stop 9 is confirmed,
and the conveyance of the abutting resonator to the adjacently located
holder 3 on the rotary indexing turn-table 2 is triggered.
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The processing stations for the resonator lie opposite indexed
positions of the holders 3, on the base plate 1 and are in a sequence
corresponding to the direction of rotation of the rotary indexing turn-table,
there being firstly a lifting station 9' provided at the end stop 9, then a
magnetization device 10, a sand-blasting frequency adjusting device 11, a
first ejection station 12 for resonators that have been adjusted to a
frequency outside the given tolerance frequency range, with a chute 13 and
a storage container 14, and finally a second ejection station 15 for
resonators that are adjusted to a frequency within the tolerance frequency
range, which likewise possesses a chute 13 and a storage container 16. An
empty station lies between the magnetization station 10 and the sand-blasting
device 11, and also between the first ejection station 12 and the second
ejection station 15, whilst five empty stations lie between the second
ejection station 15 and the lifting s~ation 9'.
The indexing process of the pneumatic rotary indexing turn-table,
which possesses twelve indexing positions, is triggered via an electro-
pneumatic valve 17 as a result of which said table rotates pneumatically
by one graduation. An incorporated hydraulic buffer prevents a violent
impact. Whereas the diameter of the rotary indexing table used in this case
amounts to 270 mm, the graduation accura;Gy amounts to -~0.03 mm. Supply of
operating and control voltages for the sand-blasting adjusting device takes
place via a plug board 18 that is arranged on a support of the guide rail 5.
Figure 2 is a side view of a holder 3 in the clamping position,
with a resonator clamped by its pin-like holding elements. The holder 3
comprises a rod-shaped, rigid, lower clamping jaw 31 which is combined with
two raised fixing plates on its lateral faces to form a unit 31' of U-shaped
cross-section, and also comprises an upper clamping jaw 32 which is rotatable
about an axis of rotation 33 mounted horizontally in the fixing plates.
Both of the clamping jaws 31 and 32 are aligned radially to the rotary
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indexing table and at their ends facing the processing stations the~ are
provided with mutually opposed horizontal clamping surfaces 34 whilst at
their opposite end they are coupled to one another via a helical pressure
spring 41 (Figure 4). The upper side of the upper clamping jaw 32 is
secured ~o one flank of a 90 elbow 35, whose free flank serves to open the
closed clamping jaws when deflected in the direction of an arrow 36. Also
the holder contains a prismatic locking component 37, which at one end is
pivoted between the fixing plates, and which is mechanically biased by a
helical spring 38 towards the end side of the upper clamping jaw 32 facing
away from the processing station, and is provided to lock the open clamping
jaw in position. This locking action occurs in that when the clamping jaws
are open, the end side of the upper clamping jaw 32 is accommodated in a
matching recess of the locking component 37.
Figure 3 r~presents the holder in a plan view, showing how the
upper clamping jaw 32 is divided by a vertical slot along its longitudinal
central plane, into two halves 32' which are rigidly connected to one another
with a given spacing by the 90 elbow 35 as a result of which each of the
pin-like hoIding elements of a resonator 39 are clamped by a respective
half 32' of the upper clamping jaw 32. Each holding element is thus
individually clamped by one half, and the clamping reliability is thus
increased.
Figure 4 il~ustrates a longitudinal section through an open holder,
in which can be seen the helical spring 41 which is inserted in a bore 40
in the lower clamping jaw 31 and is subjected to pressure towards the upper
clamping jaw 32. The end sides, facing away from the processing stations,
of the open, upper clamping Jaw-halves 32' are here locked by being
accommodated in a form-fitting recess 42 in the locking component 37 which
is biased towards these end sides by the helical spring 38.
Figure 5 is a section through the guide rail 5 in the region of
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the lifting station 9', with a resonator 39 abutting against its end stop 9,
together with a section through that part of the clamping jaws 31 and 32
which faces towards the end stop 9, in a holder 3 located opposite the
raising station. A lateral boundar~ wall 51, of the guide rail 5, facing
the holder 3, is provided in the region of the raising station 9' with a
wall level which constantly increases towards the end stop 9, so that the
resonators
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with their pin-like holding elements slide along the boundary wall
to come to rest against the end stop 9 in such manner that the ho-
lding elements slope upwards by approximately 10 in relation to the
horizontal direction.
In the following indexing step, one of the holders 3 secured
to the rotary indexing table is conducted, with the upper clamping
jaw 32 in the open position, to the position opposite to the lift-
ing station 9'. At the end of this transport step, the holder 3
assumes such a position in relation to the resonator 39 abutting
against the end stop 9 that the upwards-sloping, pin-like holding
elements of said resonator come to lie just over the edge 35 fo~ed
by the end face and the clamping surface 34 of the lower clamping
jaw 31. Then a lifting magnet secured above the holder 3 is act-
uated, which serves to tilt a prismatic locking component 37 which
ser~es to lock the open clamping jaw, as shown in Figure 3 in the
direction towards the centre point of the rotary indexing table 2,
and thus the locking of the open, upper clamping jaw 32 is discon-
tinued. The pressure of the helical spring 41 that is arranged
between the upper and the lower clamping jaws now serves to rotate
the upper clamping jaw 32 into the clamping position. The assoc-
iated movement of its clamping surface 34 in the downwards direct-
ion serves to grip the upwards-slanting, pin-like holding elements
o~ the relevant resonator that is then against the end stop, to br-
ing said resonator into the horizontal position and simultaneously
to lever it above the lever h of the end stop. The resonator, which
is thus clamped between the clamping surfaces 34 of the holder,
can now freely follow any further rotation of the rotary indexing
table.
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The cross-sectional view given in Figure 6, is in an identical
sectional plane to that of ~igure 5, but represents a resonator 39 which is
in the clamping position, and thus raised above the level h of the end
stop g.
Fi~lres 7 and 8 are sections through the magnetization station 10
secured to the base plate, Figure 7 showing the rest position and Figure 8
the clamping position required for magnetization of a resonator. The mag-
netization station 10 consists of a housing 101 which is rigidly connected
to the base plate, and which possesses a lifting magnet and two levers 104
and 105, each of which can be moved about a respective pivot, 102 and 103.
The first lever 104 is provided with an indentation 106 which serves to
accommodate that side of a resonator 39 facing away from the pin-like hold-
ing elements, and the second lever 105 possesses a half 108 which is
electrically insulated by means of a non-conductive intermediate layer 107.
This insulated part of the second lever is connected to an electrically
conductive projection 109 which is provided to clamp any relevant resonator
39 against the indentation 106. Between the housing 101 and the non-
insulated part of the second lever 105 there is arranged a helical tension
spring 110 so that the second lever 105 presses against the ~irst lever 104,
and the latter presses against an armature 111 of the lifting magnet, which
is in the rest position, and the clamp is thus open.
In the clamping position required for the magneti~ation of the
resonators, represented in Figure 8, the first lever 104 is pressed by the
armature 111, which is deflected against the force of the helical spring 110,
so ~hat the first lever lies against the second lever 105 in such manner that
the resultant turning of the two levers place causes the resonator which is
to be magnetized to become clamped between the indentation 106 of the first
lever and the conductive projection 109 of the second lever. The resonator
is thus contacted by the conductive projection 109 positioned between the
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pin-like h~lding elements and by the indentation 106 on the rear side of
the resonator which is to be magnetized, this lying opposite the support
elements. The magnetization itself takes place by causing a controlled
passage of current through the clamped resonator, between these contact
points.
Following the electronically controlled passage of current, the
helical spring 110 brings the armature back into its rest position, as
represented in Figure 7, and the two levers 104 and 105 are pivoted back into
their initial position so that the resonator can follow the further rotation
of the rotary indexing table.
Having passed through an empty station, the magnetized resonator
is conducted to the actual sand-blasting adjusting device 11 where, by the
step-by-step sand-blasting of an end face its resonant frequency is adjusted
to a given frequency, with a tolerance of -~2 Hz. As soon as the rotary
indexing table 2 has brought the resonator into the sand-blasting adjusting
device 11, a coil serves to energize the resonator, and its inherent
frequency is detected by a microphone and forwarded to a control device. In
accordance with the d~fference between the actual frequency and the pre-
determined theoretical frequency, the duration of the sand-blasting is
determined, and the sand-blasting device is then switched on. Two sand-
blasting nozzles are secured on a bridge above a suction channel and are
directed via a ball joint towards the two end faces of the oscillator in
such manner that the sand jet hits the end face at an
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angle of approximately io. When the yiven sand~b].asting time has
expired, the sand jet is switched off, and the inherent frequency of
the oscillator is again measured. These processes are repeated until
the inherent frequency lies within the given tolerance limits of
the theoretical frequency, the duration o~ application of the sand
jets generally becoming increasingly shorter from step to step. For
the removal of the blasted sand, and displaced resonator material,
the sand blasting adjusting device is connected to a suction system.
Since the resonators must be adjusted with a high degree of acc-
uracyO their inherent frequency cannot be allowed to be influencedby the suction flow. For this reason, in the suction channel a valve
is installed, which is actuated via a rotary magnet as soon as an
automatic control unit switches over for measurement. This valve
releases a side opening in the suction channel and closes off the
path between the resonator and the suction unit 80 that the resonan-
ce frequency of the resonator is not influenced by the circulatiny
air. The supply of sand for the sand-blasting process, and all the
operating sequences required for this purpose take place in a device
manufactured by the Wide Industrial Division, New York, commercially
2~ available under the name "AIRBRASIVE".
Figure 9 represents the first ejection stage 12, provided for
resonators which have been found to have a frequency outside of the
given tolerance frequency ranc3e, even after adjustment. This stage
consists of a lifting magnet 121, which is secured to the base plate,
and whose armature 122 has its longitudinal axis radially aligned
with respect to the rotary indexing table 2 t and serves to defl-
ect the free flank of the ~0 elbow 35, and thus to open any hol-
der 3 that is supporting a misadjusted resonator.
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Figure 10 illustrates the second ejection station 15, at
which the free flank of the 90 elbow 35 is deflected by a roller
152 which is rotatable about a vertical axis 151 and the relevant
holder 3 is thus opened. During the further movement of the rotary
indexin~ table, the holder 3 remains open until it returns to the
station located opposite the lifting statio:n 9'.
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