CA1047113A - Apparatus for automatic adjustment of frequency of mechanical resonators - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Apparatus for the automatic adjustment of the resonant frequency of magnetic mechanical resonators, in which conveyor means are provided to feed a plurality of resonators step by step through a demagnetiz-ation station and a magnetization station to a final measurement and processing station in which the resonant frequency is monitored whi-lst material is removed by using a sand-blasting process, the final output of the conveyor being to a selected ejection stage determined by the tuning accuracy achieved in each case.

Description

1047~3 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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71~3 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 :1~47~1L3 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 ~_ 1q3 471~3 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 B

~47~3 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.

1~71~3 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 1~47113 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 1~47~13 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 ff _g_ ~f347~13 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.

3~B I , 7~3 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 ~3 ~47113 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 '.~

7~l~3 - `
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.

B -l3-~47~3 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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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS :-

1. 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 predetermin-ed theoretical frequency by the controlled removal of resonator ma-terial using sand-blasting in dependence upon a difference frequency produced by comparison of the theoretical and actual measure frequ-ency, said resonators being conducted via a guide rail to be demag-netized, and then abut against an end stop where each resonator act-uates a switch that serves to trigger a control signal and instigate the conveyance 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, t-he resonators thus accommodated in the holders then being conveyed in sequence to individual processing stations by a step-by-step rot-ation of the rotary indexing table, a drive control unit for the ro-tary 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 magnetiz-ed, the following processing station being that in which the sand-bl-asting adjustment is carried out, and comparator means being provid-ed to store that measurement of the resonance frequency which concl-udes any sand-blasting adjustment, said stored resonance frequency then being compared with a given tolerance-frequency range, and ejec-tor means responding if its resonance frequency lies outside the gi-ven 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.

2. Apparatus as claimed in Claim 1, in which that resonator abut-ting against the end stop is gripped by means of its pin-like holdi-ng elements resting on a lateral boundary wall of the guide rail by a clamping surface of a lowering, upper clamping jaw, and further lo-wering of the clamping jaw causes that resonator to be levered above the end stop, and finally the pin-like holding elements are clamped between the opposed clamping faces of the upper and of a lower clam-ping jaw.

3. Apparatus as claimed in Claim 1, in which said rotary indexing table is arranged on a base plate and provided with said holders ar-ranged concentrically about its axis of rotation at equal intervals, said stations being arranged on the base plate opposite each indexed position of the holders, drive means for the rotary indexing table being arranged on the base plate, a vibrator device being provided to feed resonators to a guide rail which is connected to the output of the vibrator device, a photo-electric monitoring barrier being p-rovided before a demagnetization station, a lifting station being p-rovided at that end of the guide rail which lies opposite the vibra-tor device for conveying the resonators to the adjacently located ho-lder of the rotary indexing table, said lifting station possessing a raised end stop which is operatively connected to a switch.

4. Apparatus as claimed in Claim 3, in which each said holder pos-sesses a lower clamping jaw which is of rod-shaped design and is rig-idly connected to the rotary indexing table, and an opposed upper cla amping jaw which is of rod-shaped design and which is rotatable about a horizontal axis of rotation, both of the clamping jaws being prov-ided with oppositely located clamping surfaces at that of their ends facing the processing stations, and at their other ends being coupled to one another via a helical pressure spring the lower clamping jaw being provided with two fixing plates which are secured to its side faces and raised in the vertical direction at least to the level of the axis of rotation, said axis of rotation being in the form of a pin which is conducted through the upper clamping jaw and is mounted in the fixing plates, a 90° elbow being connected by one flank in ri-gid fashion to the upper side of the upper clamping jaw which serves for opening of the clamping jaws by deflection of the free flank of the 90° elbow, and a prismatic locking component provided which ser-ves to lock the open clamping jaws with one end pivoted between the fixing plates, said locking component being mechanically biased by a helical spring towards that end of the upper clamping jaw which fac-es away from the processing stations, which end is accommodated in a matching recess in the locking component when the clamping jaws are open.

5. Apparatus as claimed in Claim 4, in which that lateral boundary wall which faces the holder of the guide rail is raised relative to the central axis of a resonator when arranged in the guide rail, at least in the region of the lifting station.

6. Apparatus as claimed in Claim 4, in which the lower clamping jaw is combined with the fixing plates to form a unit of U-shaped cr-oss-section, the upper clamping jaw being divided by a vertical sec-tional plane running parallel to its longitudinal central axis to fo-rm two halves rigidly connected to one another via the 90° elbow at such a distance that the two pins of any one resonator are simultan-eously clamped by the respective halves of a holding element of a re-sonator.

7. Apparatus as claimed in Claim 3, in which said magnetization station possesses a lifting magnet which is arranged in a housing ri-gidly connected to the base plate, a first lever being movable about a fixed axis of rotation and provided with an indentation, a second lever being movable about another fixed axis of rotation, said two axes of rotation being mounted in the housing, at least one part of the second lever being electrically insulated, and possessing an ele-ctrically conductive projection which serves to clamp the respective resonators against the indentation, a helical tension spring being arranged between said housing and the non-insulated part of the sec-ond lever, in such manner that in the rest posit-ion the second lever presses against the first lever and the latter presses against the armature of the lifting magnet when in the rest position, and the clamp is thus opened, and the clamping position pr-ovided for the magnetization of the resonators being such that the first lever is pressed by the armature when the latter is deflected against the spring force of the helical spring against the second le-ver, and the resultant mutual turning of the two levers which thus takes place causing the inserted resonator to be clamped between the indentation of the first lever and the conductive projection of the second lever, after which magnetization is effected by feeding a con-trolled current between the clamping points.

8. Apparatus as claimed in Claim 3, in which the first ejection station possesses a lifting magnet whose armature has its longitudi-nal axis radially aligned to the rotary indexing table deflection of the free flank of the 90° elbow serving to open any holders contain-ing mis-adjusted resonators.

9. Apparatus as claimed in Claim 3, in which said second ejection station possesses a roller which is rotatable about a vertical axis, and which serves to open the holders by deflection of the free flank of the 90° elbow.

10. Apparatus as claimed in Claim 3, in which empty stations are arranged between individual stations.