US3823546A - Crystal-controlled digital clock - Google Patents

Crystal-controlled digital clock Download PDF

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Publication number
US3823546A
US3823546A US00235196A US23519672A US3823546A US 3823546 A US3823546 A US 3823546A US 00235196 A US00235196 A US 00235196A US 23519672 A US23519672 A US 23519672A US 3823546 A US3823546 A US 3823546A
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Prior art keywords
timepiece
motor
wheel
frequency divider
digit
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Expired - Lifetime
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US00235196A
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English (en)
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B Gortz
W Fehrenbacher
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Kieninger and Obergfell GmbH and Co
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Kieninger and Obergfell GmbH and Co
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Priority claimed from DE19712112691 external-priority patent/DE2112691A1/de
Priority claimed from DE19722210700 external-priority patent/DE2210700A1/de
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    • G—PHYSICS
    • G04—HOROLOGY
    • G04C—ELECTROMECHANICAL CLOCKS OR WATCHES
    • G04C17/00—Indicating the time optically by electric means
    • G04C17/0075—Indicating the time optically by electric means by drums or drum-like devices
    • G—PHYSICS
    • G04—HOROLOGY
    • G04F—TIME-INTERVAL MEASURING
    • G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
    • G04F5/04—Apparatus for producing preselected time intervals for use as timing standards using oscillators with electromechanical resonators producing electric oscillations or timing pulses
    • G04F5/06—Apparatus for producing preselected time intervals for use as timing standards using oscillators with electromechanical resonators producing electric oscillations or timing pulses using piezoelectric resonators

Definitions

  • a clock with coaxial digit wheels for one-minute, tenminute and hour indications has a drive motor intermittently energized by an electronic switch constituting the final stage of a 20-stage binary frequency divider which is stepped, at a frequency of 2 /60 112, by a crystal-controlled oscillator.
  • the latter consists essentially of a dual-PET inverter of MOS type connected across a quartz crystal, similar inverters being used for the several stages of the frequency divider.
  • a holding button or key may be manually operated to apply a zero-setting potential to all the stages for ar resting the clock until the actual time matches its reading.
  • References Cited and its battery-operated driving circuit may be UNITED STATES PATENTS mounted as a detachable unit on the clock housing.
  • Our present invention relates to a digital clock of the crystaLcontrolled type wherein two or more digit wheels are operatively interconnected, advantageously in coaxial relationship, to display time indications of different denominational orders in a window of a housing such as the units and tens digits of the minutes and corresponding numerical values for the hours.
  • the degree of accuracy of such a timepiece depends upon the precision with which a predetermined steppingpulse cadence can be maintained.
  • the use of mechanical synchronizing means such as a balance Wheel even when coupled with an inherently stable pulse generator such as a crystal-controlled oscillator, is not entirely satisfactory since the intermittently advancing clockwork subjects the synchronizing mechanism to shocks which may throw the system out of step.
  • conventional devices of this character are relatively bulky and difficult to operate from a low-voltage power supply such as a flashlight battery or dry cell.
  • the general object of our invention is to provide an improved timepiece of the aforedescribed type, especially a portable clock, which avoids the drawbacks set forth and operates reliably over extended periods with no maintenance other than a possible replacement of batteries.
  • a more particular object is to provide a steppingpulse generator of low power consumption for a miniature electric motor driving the lowest-ranking digit wheel of such a timepiece.
  • the drive motor of the timepiece is periodically stepped by the output of a pulse generator which includes a crystal-controlled oscillator and a frequency divider energized thereby, this divider converting the crystal-stabilized oscillations into a succession of stepping Pulses each occurring during a unit of time (e.g.
  • each stepping pulse lasting for only a fraction of such a unit of time, energizes the motor long enough to drive a rotary member, positively coupled with its rotor, through part of a revolution whereupon a homing circuit controlled by that member keeps the motor operating until the revolution is completed.
  • a homing circuit may include a pair of cam-operated contacts closing the motor circuit near the trailing edge of the stepping pulse forming part of a square wave emitted by a flip-flop which constitutes the final stage of the frequency divider.
  • a Geneva-type transmission drivingly engaging a co-operating element over only a fraction of its own revolution.
  • a transmission advantageously, includes a sector gear as the driving member and a full gear as the driven element, a concentric dwell on the sector gear serving to arrest the driven gear in the position last reached upon its entrainment by the toothed portion of the driving gear.
  • the miniature drive motor together with its homing circuit forms part of a unit which is detachably mounted on the digitwheel housing, the associated pulse generator being carried on the housing as an integrated module and being electrically connected to the motor circuit through flexible conductors which are long enough to enable physical detachment of the driving unit from the housing.
  • either component may be made accessible from all sides for the purpose of inspection or repair.
  • a further feature of our invention resides'in the provision of a manually operable switch which is preferably carried on the detachable unit and serves for the temporary deactivation of the stepping-pulse generator to resynchronize the clock by arresting the digit wheels in the position in which they happen to be or into which they are manually moved; at the instant when this wheel position corresponds to the actual time, e.g. as indicated by a radio signal, the user restores the switch to restart the clockwork.
  • a particularly efficient oscillator for our improved motor drive comprises a pair of complementary field effect transistors with a common gate lead and a common drain lead connected to opposite terminals of a frequency-stabilizing crystal, hereinafter referred to simply as quartz.
  • the two complementary F.E.T.s which may be of the monolithic type known in the art as COS/MOS, constitute an inverter whose output is fed back to the quartz to establish a voltage difference thereacross. With the gate lead biased at an intermediate potential by two identical resistors extending from that lead to respective source electrodes of the two F.E.T.
  • a pair of storage capacitors inserted between the two quartz terminals and a point of fixed potential (such as one of the two source electrodes) will alternately acquire positive and negative charges in the rhythm of the natural frequency of the quartz as modified by a trimmer condenser in series therewith.
  • a trimmer condenser in series therewith.
  • Pairs of similar inverters may be included in respective stages of the binary frequency divider following the oscillator. All these components can, therefore, be readily accommodated on a printed strip mounted on the digit-wheel housing, preferably on a rear wall of that housing parallel to the wheel axis.
  • a miniature drive motor stepped by such a frequency divider through an amplifier advantageously including two cascaded complementary transistors, can be operated with a conventional battery of, say, 1.5 V; the slightly higher voltage requirements of the oscillator, the frequency divider and the input circuits of the cascaded transistors can be satisfied by a separate battery of about 6-9 V. Since the energy consumption of the electronic components is small, excess power will be available to operate ancillary equipment such as, for example, an alarm circuit.
  • FIG. 1 is a front elevational view (with parts broken away) of a timepiece embodying our invention
  • FIG. 2 is a bottom view of the assembly of FIG. 1;
  • FIG. 3 is an exploded perspective view of the digital clockwork of the timepiece shown in FIGS. 1 and 2;
  • FIG. 4 is a circuit diagram of the motor drive for the clockwork
  • FIG. 5 shows details of an oscillator included in the diagram of FIG. 4
  • FIG. 6 is an end view of a modified driving unit for a timepiece according to our invention.
  • FIG. 7 is a side view of the unit illustrated in FIG. 6;
  • FIG. 8 is a top view of the same unit
  • FIG. 9 is a detail view of part of the power train of the drive unit as seen from above, drawn to a scale larger than that of FIG. 8;
  • FIG. 9a is a face view of a homing cam also seen in FIG. 9;
  • FIG. 9b is a face view of a driving gear seen in FIG. 9 and of a coacting driven gear
  • FIG. 10 is a top view, drawn to a smaller scale than FIG. 8, of an entire timepiece provided with the unit of FIGS. 6 8.
  • FIGS. 1 and 2 we have shown parts of the housing of an electric digital clock including a bracket l with two upstanding arms 2, 3.
  • This housing has a window, not shown, for displaying the time of day (here 16:36 hours or 4:36 PM) in the form of digits carried by three coaxial wheels 4, 5 and 6.
  • Digit wheel 4, bearing the numerals 0 to 9, and digit wheel 5, bearing the numerals O to 5, show the minutes;
  • digit wheel 6 displays the hours with the aid of eight peripherally mounted prismatic bodies of which three, designated 8, 9 and 10, are visible in FIG. 1.
  • Bracket 1 supports, via posts 13 and screws 14, a similar, smaller bracket 15 having upstanding arms 16 and 17.
  • the arm 3 of bracket 1 is broadened to serve as a mounting plate for a motor 22 and other parts of the stepping drive, the motor having a base 31 supported on plate 3 by posts 21.
  • Digit wheels 4, 5 and 6 are rotatably journaled on three fixed shafts 19, 18 and 7, respectively.
  • Shaft 7 extends between uprights 2 and 16; shaft 18 spans the arms 16 and 17 of bracket 15 which lie within the concave sides of the two hollow wheels 6 and 4, confronting the intermediate wheel 5, while shaft 19 is secured to uprights 17 and 3 in line with shaft 7.
  • the two aligned shafts 7 and 19 are offset from shaft 18 by a distance equal to the difference between the radii of the two larger wheels 4, 6 (which are of like diameter) and of the smaller wheel 5 whereby the centrally disposed faces of the polygonal peripheries of the wheels 4, 5 and 6 as viewed in FIG.
  • Wheel 5 is also laterally recessed, as seen in FIG. 3, so as to have two overhanging rims 111, 136 corresponding to a rim on the concave side of wheel 6 and a similar rim on the confronting face of wheel 4.
  • the spaces framed by rim 100 of wheel 6 and by the corresponding rim of wheel 4 serve-to accommodate indexing means constituted, in the case of wheel 6, by a ratchet 101 normally engaged by a pawl 103 which is swingable about a fulcrum 104 and has its free end 105 stressed by a tension spring 107 anchored at 106 to the body 102 of the digit wheel.
  • the analogous indexing mechanisms for wheels 4 and 5 have not been illustrated.
  • an escapement lever on the remote face of wheel 5 is integral with an axially extending projection or dog 110 which is normally held by a loading spring against the inner peripheral surface of rim 111 so as to lie in the path of a set of cooperating projections 109 of wheel 6 formed as internal ribs on the rim 100 thereof.
  • Similar projections 130 in the shape of prismatic studs, extend axially from the inner periphery of rim 136 of wheel 5 into the concave side of wheel 4 for coupling engagement with a single dog I31 fixed within that side to the rim of the latter wheel.
  • ratchet 101 and the corresponding ratchet of wheel 5 have eight and six teeth, respectively; similarly, there are eight projections 109 on wheel 6 and six projections on the wheel 5.
  • wheel 5 is stepped once per revolution of wheel 4 through an angle of 60 whereas the wheel 6 is advanced once per revolution of wheel 5 through an angle of 45.
  • the stepping drive for wheel 4 includes, besides the synchronous motor 22, a gear train 23-30; if this drive comprises a stage with positive immobilization of the load, such as a Geneva motion or the equivalent transmission described hereinafter with reference to FIG. 9b, the
  • the presence of the lever carrying the dog 1110 has the effect of an overrunning clutch by permitting the hour wheel 6 to overtake the ten-minute wheel 5 on being manually rotated (clockwise as viewed in FIG. 3) to change the hour indication, with the projections 1109 camming aside the projection 1110 by bearing upon a beveled outer face thereof if the latter projection happens to lie between the two foremost ribs 109', 1109" of wheel 6 as illustrated in FIG. 3, i.e., if wheel 5 occupies the 50-minute position in which its next step would advance the wheel 6 from, say, the ll-oclock to the l2-oclock position.
  • a manual advance of l-minute wheel 4 may also step the 10-minute wheel 5 and possibly the hour wheel 6, in the same way as does the automatic drive described below.
  • the range of positive entrainment of wheel 5 by wheel 4 and of wheel 6 by wheel 5 may be somewhat less than 60 and 45, respectively, inasmuch as the force of loading spring 107 and its counterpart will in such case complete the rotation of the follower wheel through the desired angle.
  • Digit wheels 4 and 6 are shown provided with toothed peripheries 64 and 65 facilitating the setting of the minute and hour indications, e.g. with the aid of nonillustrated pinions meshing therewith and projecting from the housing for manual actuation as described in the aforementioned US. Pat. No. 3,685,280.
  • Motor 22 has an operating circuit, more fully illustrated in FIG. 4, including a normally open homing switch 33 in the form of contact springs riveted at 36 in mutually insulated relationship to a stud 37 which projects from mounting plate 3.
  • a normally open homing switch 33 in the form of contact springs riveted at 36 in mutually insulated relationship to a stud 37 which projects from mounting plate 3.
  • One of the contact springs forms a tongue 34 bearing upon a rotary cam disk 35 on the shaft of transmission gear 30.
  • Cam 35 more fullydescribed below with reference to FlG. 9a, has a dwell which closes the contacts 33 whenever the motor 22 is briefly energized by the pulse generator of FIG. 4 to rotate the gear and its shaft through an arc of, say, a quarter of a circle. Closure of the homing circuit then maintains the motor operated until the cam has performed a full revolution.
  • the step-down ratio of the gear train 23 30 is so chosen that such a revolution drives the wheel 4 through an arc of 36, corresponding to its peripheral subdivision by the 1- minute markings.
  • the motor speed is advantageously so regulated that a revolution of cam 35 lasts somewhat less than a minute so that the motor will be restarted by the next stepping pulse after a rest period which may vary with the supply voltage and other external parameters.
  • Homing contacts 33 are representative of a variety of switches that can be used for this purpose, e.g. reed switches responsive to a pair of magnets of opposite polarity mounted with the requisite angular spacing on a disk replacing the cam 35.
  • FIG. 4 shows the electronic components serving for the intermittent energization of motor 22.
  • These components include an oscillator 40 consisting essentially of a quartz 0, an inverter $0, a pair of storage capacitors C C and a trimmer condenser C in series with the quartz Q.
  • the oscillator 40 is con nected across a supply battery of 9 V whose terminals are tied to a positive bus bar 411 and a negative bus bar (here grounded) 4-2; a current-limiting resistor R is inserted in bus bar 411.
  • a voltage divider consisting of two substantially identical resistors R R whose junction, biased to an intermediate d-c potential of about 4.5 V, feeds a gate lead 43 of inverter SQ which is constituted by two complementarily symmetrical monolithic semiconductors COS/MOS, specifically field-effect transistors.
  • Quartz Q and trimmer condenser C lie between the gate lead 43 and a common drain lead 44 of the two F.E.T.s which in FIG. 5 have been designated P and N according to their respective conductivity types.
  • Capacitor c lies between negative bus bar 42 and the drain lead 44 connected to one terminal of quartz Q.
  • Capacitor C lies between the same bus bar and the other quartz terminal (in series with condenser C being thus arranged in parallel with resistor R This oscillator can operate with high frequency stability even in a range as low as a few kHz.
  • This frequency is stepped down by two cascaded multistage frequency dividers ST and 5T of 14 and 6 binary stages, respectively, there being thus a total of 20 stages with a resulting step-down ratio of 1:2
  • Each divider stage advantageously is a flip-flop with a pair of inverters of the COS/MOS F.E.T. type, similar to circuit SQ, cross-connected in the conventional manner for bistable operation.
  • Each of the two inverters of each stage has its common drain connected to a respective lead 144', 1144" and 244 (corresponding lead 44 of FIG. 5), 244".
  • the leads 1144' and 244 of all stages are permanently grounded at bus bar 42 whereas the companion leads 1144" and 244 are connected to ground through a manually operable switch 45 and further connected through a large resistor R, to positive bus bar 411.
  • switch 45 With switch 45 in its normal closed position, the inverters with drains tied to conductors 144" and 244" operate in the same manner as the inverter SQ of FIG. 5 so that the respective flip-flop counts the incoming pulses or voltage surges from the preceding stage or from oscillator 40. If, however, switch 45 is opened, the drains of the affected inverters go positive so that all the stages are reset to and maintained in what may be considered their 0" condition. This interrupts the pulse train on output lead 46 so that motor 22 is no longer stepped.
  • connection between lead 46 and motor 22 includes a coupling condenser C in the input of a first amplifier stage constituted by a PM? transistor T the emitter of this transistor being connected directly to bus bar 41 and to its base through a voltage divider R R whose junction is tied to condenser C
  • the collector of transistor T feeds, through a resistor R the base of an NPN transistor T constituting a second amplifier stage; the emitter of the latter transistor is grounded at bus bar 42 whereas its collector is connected through the field winding of motor 22 to an ancillary bus bar 47 which is maintained by another battery at a potential of +1.5 V.
  • a resistive and capacitive braking circuit for motor 22 may be completed by the switch 33 upon the reopening of the homing circuit to prevent the motor from overshooting the home position of cam 35.
  • FIGS. 6 10 we have shown a demountable unit 50 containing the motor 22 with its housing, cam 35 and part of the transmission by which this motor is coupled with the digit wheels 4 6.
  • a mounting plate 200 adjoining the plate 3 of the digit-wheel housing 236, is detachably secured to the latter plate by elastic studs 222 held in position thereon by screws 224, the studs 222 passing through complementary apertures 223 of plate 200 in frictional engagement therewith.
  • Bolts 201 provided with nuts 202, spacedly support an ancillary plate 203 on plate 200.
  • a bracket 204 secured to plate 200 by screws 205 (only one shown), carries the drive motor 22 whose vertical shaft 206, lying skew to the axis of wheels 4-6, has keyed to it a worm 23 forming part of the transmission 23 30 of FIGS. 1 and 2.
  • Shaft 210 further carries the cam disk 35 as well as a sector gear 30a, more clearly illustrated in FIGS. 9 and 9b, which intermittently drives another spur gear 30b also seen in FIG.
  • sector gear 300 is rigid with spur gear 27 with which it may have been integrally molded from plastic material.
  • the toothed portion 230 of this gear extending over less than half its circumference, adjoins a cylindrical portion 226, centered on the axis of shaft 210, which in the home position engages two neighboring teeth of driven gear 30b so as to prevent rotation of the latter.
  • Cylindrical gear portion 226 is axially extended toward cam 35 so as to complement a part-cylindrical hub portion 227 of the latter whereby the disk 35 is positively coupled with the integral assembly 27, 30a for joint rotation. Axial separation of hub portions 226 and 227 is prevented by a washer 48 held in position by a cotter pin not shown.
  • cam 35 includes a low dwell 241 extending over approximately a rising flank 243 leading therefrom to a high dwell 242 which spans about and a radial edge 240.
  • tongue 34 is lifted onto dwell 242 to close the contacts 214, 217 well before the stepping pulse then energizing the motor 22 has terminated. Continuity of rotation is thus assured until the tongue 34 drops off the edge 240, thereby instantly opening the motor circuit and arresting the cam. Since the concentric portion 226 of driving gear 300 immobilizes the driven gear 30b at this stage of the cycle, the operation of the clockwork is not affected by minor departures of the cam 35 from its theoretical home position.
  • the number of teeth of gear portion 230 depends, of course, on the transmission ratio of the coupling between shafts 212 and 19 which may include a ratchet drive to facilitate manual setting of wheel 4 with the gear 36b blocked.
  • a single tooth may suffice in a limiting case.
  • the elements mounted on plate 200 are electrically connected to a printed strip 229, carrying the components 40, ST,, 8T T and T of FIG. 4, through flexible conductors 228 which enable the physical separation of unit 50 from the digit wheels 4 6 without detaching the strip 229 from the clock housing 236 on which it is mounted.
  • the strip 229 extends along the rear wall of the housing, parallel to the wheel axis, on the side remote from the window through which the digit wheels can be read.
  • the battery or batteries used to power the motor circuit may be accommodated on the clock housing 236 or on the detachable unit 50.
  • a time piece comprising:
  • a set of operatively interconnected digit wheels including a first wheel provided with time indications of a relatively low denominational order and a second wheel provided with time indications of a relatively high denominational order;
  • drive means including a rotary member, a motor positively connected with said member and a power source for said motor;
  • a generator of stepping pulses for said motor energized by said power source said generator including a crystal-controlled oscillator and a frequency divider energized by said oscillator to deliver to said motor a succession of stepping pulses each occurring during a unit of time of said low denominational order and lasting long enough to rotate said member through a fraction of a revolution;
  • homing means coupled with said motor for maintaining same energized from said power source beyond the duration of said stepping pulse to drive said member through a full revolution within said unit of time, said coupling means translating said full revolution into an advance of said first wheel by one time indication.
  • a timepiece as defined in claim 3 wherein said homing means comprises a cam coaxially mounted with said driving gear for joint rotation therewith and contact means actuatable by said cam in an off-normal rotary position thereof.
  • a timepiece as defined in claim Ill further comprising a worm directly connected with said motor, a worm gear in mesh with said worm and a set of intermeshing spur gears transmitting the torque of said worm gear to said member, said worm gear and said spur gears being rotatable about axes parallel to said digit-wheel axis.
  • a timepiece as defined in claim 1 wherein said oscillator comprises a pair of complementary fieldetfect transistors with a common gate lead and a common drain lead, a frequency-stabilizing crystal between said leads, and a direct-current power supply connected between respective source electrodes of said transistors.

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US00235196A 1971-03-16 1972-03-16 Crystal-controlled digital clock Expired - Lifetime US3823546A (en)

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Application Number Priority Date Filing Date Title
DE19712112691 DE2112691A1 (de) 1971-03-16 1971-03-16 Quarzuhr mit Digitalanzeige
DE19722210700 DE2210700A1 (de) 1972-03-06 1972-03-06 Quarzuhr mit digitalanzeige

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959744A (en) * 1975-02-26 1976-05-25 Time Computer, Inc. CMOS oscillator having bias circuit outside oscillator feedback loop
US4037402A (en) * 1974-03-29 1977-07-26 Licentia Patent-Verwaltungs-G.M.B.H. Circuit arrangement for a quartz controlled electrical clock
US4176517A (en) * 1974-09-30 1979-12-04 Citizen Watch Co. Ltd. Integrated circuit for timepiece
US4270199A (en) * 1974-05-08 1981-05-26 Sharp Kabushiki Kaisha Switching mechanism for electronic wristwatch
US4441825A (en) * 1975-09-08 1984-04-10 Citizen Watch Co., Ltd. Low-power integrated circuit for an electronic timepiece
US4937798A (en) * 1988-04-16 1990-06-26 Hengstler Gmbh Elapsed-time meter
US5581520A (en) * 1994-01-18 1996-12-03 Electrodynamics, Inc. Watch driven elapsed time indicator apparatus and its method of manufacture and use
US20130187453A1 (en) * 2011-11-22 2013-07-25 Quantum Fuel Systems Technologies Worldwide Inc. Fishtail Packaging and Cooling

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3590571A (en) * 1970-02-02 1971-07-06 Bunker Ramo Digital clock seconds indicator
US3603073A (en) * 1969-03-26 1971-09-07 Tokai Rika Co Ltd Electric timepiece

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3328954A (en) * 1965-04-22 1967-07-04 Mendell E Miller Electronic digital readout time indicating device
FR1517115A (fr) * 1966-02-10 1968-03-15 Suisse Horlogerie Montre électronique

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3603073A (en) * 1969-03-26 1971-09-07 Tokai Rika Co Ltd Electric timepiece
US3590571A (en) * 1970-02-02 1971-07-06 Bunker Ramo Digital clock seconds indicator

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4037402A (en) * 1974-03-29 1977-07-26 Licentia Patent-Verwaltungs-G.M.B.H. Circuit arrangement for a quartz controlled electrical clock
US4270199A (en) * 1974-05-08 1981-05-26 Sharp Kabushiki Kaisha Switching mechanism for electronic wristwatch
US4176517A (en) * 1974-09-30 1979-12-04 Citizen Watch Co. Ltd. Integrated circuit for timepiece
US3959744A (en) * 1975-02-26 1976-05-25 Time Computer, Inc. CMOS oscillator having bias circuit outside oscillator feedback loop
US4441825A (en) * 1975-09-08 1984-04-10 Citizen Watch Co., Ltd. Low-power integrated circuit for an electronic timepiece
US4937798A (en) * 1988-04-16 1990-06-26 Hengstler Gmbh Elapsed-time meter
US5581520A (en) * 1994-01-18 1996-12-03 Electrodynamics, Inc. Watch driven elapsed time indicator apparatus and its method of manufacture and use
US20130187453A1 (en) * 2011-11-22 2013-07-25 Quantum Fuel Systems Technologies Worldwide Inc. Fishtail Packaging and Cooling
US9622384B2 (en) * 2011-11-22 2017-04-11 Quantum Fuel Systems Llc Fishtail packaging and cooling

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GB1390457A (en) 1975-04-16
CH556569A (is") 1974-11-29
CH384072A4 (is") 1974-05-15
FR2130335B1 (is") 1976-10-29
FR2130335A1 (is") 1972-11-03

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