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Publication numberUS2671268 A
Publication typeGrant
Publication dateMar 9, 1954
Filing dateJul 30, 1949
Priority dateJul 30, 1949
Publication numberUS 2671268 A, US 2671268A, US-A-2671268, US2671268 A, US2671268A
InventorsCrawford Howard E
Original AssigneeCrawford Howard E
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Foot control for dental engines
US 2671268 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

March 9, 1954 H. E. CRAWFORD FOOT CONTROL FOR DENTAL ENGINES 4 Sheets-Sheet 1 Filed July 30, 1949 VENTOR W ATTK m Z BY g Marcfi 7E5 1 H. E. CRAWFORD FOOT CONTROL FOR DENTAL ENGINES 4 Sheets-Sheet 2 Filed July 30. 1949 March 9, 1954 CRAWFORD 2,671,258

FOOT CONTROL FOR DENTAL ENGINES Filed July 30, 1949 4 Sheets-Sheet 5 IN VEN TOR,

March 9, 1954 H. E. CRAWFORD FOOT CONTROL FOR DENTAL ENGINES Filed July 50. 1949 4 Sheets-Sheet 4 II E-11- TIE-1Z- Patented Mar. 9, 1954 UN ITED STATES PATENT OFFICE FOOT "CONTROL FOR. DENTAL ENGINES Howard-E. Crawford, Toledo, Ohio ApplicationiulyBll, 1949, SerialNo. 107,740

rl l-nqlaims. (Cl. 32-23) This invention relates to a foot control for dental engines.

An object of this invention is to provideafoot operated switch system which permits adentist to stand with both feet firmly :on the supporting plane, retaining a comfortable posture while working, and retain full control of the dental engine which entersinto th-e performance of a major portion of dental operations.

Another object ofthis invention is to provide a foot controlled switch for the circuit of a dental.- engine, which swltchmay be manipulated by a slight turn of the foot. The operator, through foot manipulation, has full control of the dental engine, imparting at will every function normally ifurnishing tool control by the engine.

vAnother object of this invention.- is to provide a switch mechanism for the full control of a dental engine which permits the operator to stand thereon and intentionally control the same, yet may be inadver-tentlystepped upon without imparting-operation-or damage to the engine 01' to the "system.

Another object of this invention is "to provide a switchmechanism which-maybe operated to select aspeed for the dental engine, repeatedly operated :to cause the engine to runat the same speed or manipulated to change the speed.

Another object of this invention is to provide a switch mechanism'for the circuit of adental engine which'permits anoperator to-select'a' speed of operation, determine the direction of rotation and automatically brake the rotation to stop following each selected and controlled function.

And another object of thisinvention is -to providea switch mechanism which is readily accessible-to the operator when needed but will not introduce a stumbling hazard to himself -or to a patient as they move. normally :aboutthe-dental chair.

Heretofore inthe general practice of dentistry, the dentist has been 'forcedto work while maintaining an unnatural Orrather a strained posture, that is supporting the major "portion of his weight on one foot in ordertoleave the-other foot free to operate a 'switchmechanism-which in turn controlled" his engine. By-thisinvention, one 01 more switch mechanisms of 'the type-disclosed may "be inserted into thefioor about the dental chair, or maybe' built'into 'a mat horizontally placed adjacent the chair, whereby the dentist :can distribute his weight 'to both feet and operate ;the switch with either foot, retain- .ingifull :control :of "the-engine "and" increasing his 2 freedom of operation. Thus fatigue is lessened and occupational diseases, heretofore attributed to the strained stance, are materially'decreased.

A plurality of the switch mechanisms may be disposed aboutachair in such a manner that the dentist may operate upon a patient from the most convenientposition, while retaining-full control oi-his engine driven-tools, with no interference from the switches nor their connections.

Other objects and advantages to be derived from this invention resulting from the'arrangement, operation and function of the related elements in the structure, tovarious details of construction, to combinations of parts and to economies of manufacture, will be apparent to those skilled in the art upon consideration of the-followingdescription and appended claims, reference being had to the accompanying drawings forming a part of this'specification wherein like reference characters designate corresponding parts in the several views.

Referringto the drawings:

Fig. 1 is a-perspective view of a'dental chair showing a typical installation and embodying features of the invention herein;

Fig. 2 is a view on the line II-II, Fig. 1;

Fig. 3 is aside elevation of a link-in the articulated mounting for a dentists hand-piece including a hook upon which the hand-piece maybe placed when notin use and including a switch housing for a hook operated switch;

Fig. 4'is an enlarged view ofthe switchportion of the hand-piece hanger of Fig. 3, the cover being removed exposing details of the switch operating mechanism;

Fig. 5 is a plan view of a foot controlled switch mechanism of the invention herein, 'parts'being broken away;

Fig. 6 is a view similarto Fig. 5, with the-control pedal broken away, and the switch-parts-in a forward speed position;

Fig. 7-is a viewon the line VII-VILFig. '5;

"Fig. 8 is a view similartoFig. ,6, with the switch parts in reverse position;

*Fig. 9 is a'detail'similarto Fig. '7, interlocked for indexing;

-Fig.'10 isa wiring diagram of a dental engine circuit'incorporating a plurality of controlswitch mechanisms;

-Fig. 11 isa plan'view .of a modified jform of the switch mechanism; and

Fig. 12 is a wiring diagramotadental engine circuit incorporating .a single control switch with the ,parts mechanism of; the type illustratedin Figgll.

Dental chair"20 is shown with the usual adjacent accessory pedestal 22, with its column 24 mounting the dental engine 2% from which artic ulated power transmission support 28 extends to carry hand-piece 30. This hand-piece embodies a chuck for the mounting of the various tools employed in the art of dentistry, the proper operation thereof requiring a critically controlled speed, direction of rotation, and brake of rotation, all instantaneously responsive to the operator.

When the hand-piece is not in use, it is hung upon hook 32 pivotally mounted. and extending from housing 34, which housing, for convenience, forms a portion of the articulated structure 28 extending from the engine 26to the hand-piece, I

the utility of this construction being more fully discussed hereafter in connection with the electric circuit for the engine 26.

The demands of present dentistry call for a dental engine, referred to in the profession as such, which in reality is an electric motor having a plurality of speeds in both directions of rotation, and in operation having an instantaneous brake to stop the rotation upon each deenergization of the armature circuit in the motor.

For purposes of illustration, the motor 28 herein is shown as having four speeds, forward or reverse, determined by suitable shunts 36, 30, and 42 placed in the circuit thereto. The

value and number of the shunts are pre-selected and for convenience may be disposed in a housing 44 accessibly mounted within the pedestal 22. The shunt 36 is a permanent protective shunt and fixes the maximum speed at which the motor can run.

The wiring necessary for satisfactory operation of the circuit is placed in conduits substantially concealed Within the equipment so that there is no interference with the operators technique.

The lines which extend to the foot controlled switch mechanism may be placed Within a conduit 46, extending from the pedestal 22 into and through floor mat 48, while a flexible conduit 4i extends from the pedestal along the support 28 into the housing 34.

a The floor mat is preferably a resilient pad, a typical construction including a sponge rubber base 50, topped with a layer of linoleum or a like wear surface 52. The mat has a feathered perimeter 54 bounding a predetermined area about the chair 20 encompassing the floor space used by the dentist while operating upon a patient in the chair. This provides a comfortable continuously horizontal level footing and allows for a decorative floor pattern.

One or more of the foot controlled switch mechanisms of the invention herein are conveniently positioned in the pad about the chair.

A preferred form of the switch mechanism includes a sheet metal cup-shaped member 56 embedded in the pad and to which the conduit 46 extends with the lines therefrom distributed about the chamber 58 within this housing to properly interconnect the various elements disposed therein.

This member 58 may have its bottom 60 resting on the floor 62 which supports the mat thereby providing a substantial foundation. The rim 64 of this cup mounts a peripheral ring 66 having its upper face 68 substantially flush with the wear surface of the mat and having an inwardly and downwardly dished portion TI] terminating in a trough 12 about central opening 14 into the chamber 58. This ring 66 may overlap and ail) squeeze the edge of the mat about this switch housing to provide a trim appearance and a continuous face from the mat to the operating element is of the mechanism. The edge of the mat about the cup may be clamped between the ring 66 and cup by means of bolts I8.

The operating element I6 includes a resilient dome-shaped shell set in a revoluble frame 82 havinghub 84 mountedon roller bearing 85 in turn mounted on staff oraxle 88 upwardly extending centrally in the chamber 58 from the bottom 60 of the member 56. The frame 82 is provided with a peripheral overhang 98 above the trough I2 cooperating therewith to keep the chamber 58 free from foreign matter entering thereinto by way of the opening 14.

Coaxially mounted about the hub 84 and spaced therefrom'is a bearing ring 92 serving as an axle for flanged ring 94 to rotate thereon. This ring 94 has a cam 96 fixed therewith together with a ratchet or toothed wheel 98 superimposed thereon. Rotation of the member 98 therefore rotates the cam 96. This cam is provided with a number of detents I00 in its periphery. The number of detents depends upon the number of switches to be operated thereby. Herein there are involved three cam operated switches I02, I 04 and I055. The operation demanding only one switch to be closed at a time, the number of detents is seven. This positions the detents so that only one of the switches I02, I04 or I06 is closed at a given time, and rotation of the cam 96 will close such switches in sequence, that is switch I02 first, then switch I04, then switch I06, and when any one is closed, the other two are open. Durin the change, all switches in this bank may be momentarily open. Adjustments as to the switches result in a smooth opening and closing sequence, one flowing into the other.

A step by ste rotation of the cam 96, as driven by the member 98, operates this speed-control bank of switches to determine the cutting in and out of the shunts 88, 40 and 42.

Rotation of the cam 96 is controlled by foot operation against the dome 80. The dentist desiring to operate the engine, assumes a natural stance with both feet on an even level upon the platform 48, shifts either foot onto the dome 80 and lifts the hand-piece 30 from the hook 32. The sequence of these operations is immaterial. A resultant automatic lifting of the hook 32 causes switch I08, within the housing 34, to close. This switch I08 is in power line IIO feeding the circuit, while the other power line II2 into the circuit includes the motor field winding.

Pressure against the pad or dome 80 depresses the same, or rather the central portion thereof, against the resistance of leaf spring II6, having one end thereof fixed to the frame 82 and the other or free end abuttin against the underside of the dome. The dome itself is a self-supporting elastic shell with a corrugated or ribbed exposed surface to be engaged by the undersurface of a foot and the spring H6 in addition to serving as an auxiliary support and reset aid also operates additional mechanism. A flexible extension H8 is attached to the free end of the spring with the extensions remote or outer end terminating in a flanged offset I20 extending downwardly through slot I22 into the chamber 58. A depression of the dome against the resistance of the spring imparts a radial and downward thrust to the flange I20. The downward movement is interrupted by the flange abutting flexible wing I24 of pawl element I26 pivotally mounted on pin I28 anchored in the frame a: for mcvemenI; therewith and normally held ii). non-ratchet engaging position by spring I 29 mounted about'the pm 128.

The first depression and rotation of the dome does not afiect the "motor circuit speed switch bank. Depression of the come onl does not affect the motor "circuit in any manner 'b'utmerely shifts the flange I20 to abut the wing I24 with the extension II8 placed under tension. Thereforeit is obvious, walking over the mat and inadve'rtently stepping on the dome does not operate nor injure the mechanisms.

The dentist rotates the dome in a clockwise direction if he wishes to run the engine forward and he rotates the dome in a counterclockwise direction if he desires the engine to run in "reverse.

A rotation of the frame clockwise simultaneously accomplishes several controls. The Wing I24 slides along pin I30 mounted on thecup bottom 60, causing the wing to be swung inwardly .and from under the flange I and the extension H8 springs the flange into interlocking engagement with the wing to hold it in its inward position until pressure on the dome is relieved.

The pawl element 1-26 does not engage the member 98 until swung into engaging position by pin I during the first clockwise rotation of the frame and the =co-relation of pin I30 and pawl element I26 and wing I24 is such that pawl I26 is not brought into engagement with the toothed member 98 until after it has cleared the indexing or driving tooth that it would normally have engaged if it had been held in ratchet engaging position by the flanged offset I20 at the start of the rotation movement. Successive swivels, if in the meantime, the wing I24 has not been freedirom the flange I20 by a lifting of the operators foot, will cause the pawl I26 to drive the ratchet step by step thereby changing the operating relationshipof the speed-control switches. The first depression and turn of the foot does not change the speed of the motor but causes the motor to run at the same speed at which it was operating in its previous run, so a dentist following each cut out of the engine 'by ting each step and a spring finger I34 positioned toengage the member I26 and prevent indexing of more than one tooth when the pedal is moved from neutral or zero in a clockwise movement.

The frame 82 includes a peripheral skirt I36 surrounding the speed control switches and in coaxial relationship with the axle88,'which skirt is provided with cam regions I30, I40, I 42 and I for operating a group of switches I46, I48, I50 and I52, in turn controlling functions'of the motor 26 other than speed variation. For example switches M6 and I48 may be operated to reversethe motor, switch I50 to cut inthe'armature brake shunt and coupler switch I52 to connect the common speedcontrol shunts in series with any of the switch mechanisms disposed about the platform or rather interconnect the 'particular switch in operation with'the shunts.

with each clockwise shirt or the frame, the switch -1'52 closes to connect the spe'edfswitch bank of the pedal being operated into -the circuit, the brake switch I 50 opensthe 'shunt 'across the armature, whilethe reverse "switches I IISan'd I38 retain their polarity.

In -a counter-clockwise shift, the switches I52 and I50 operate in the same manner but the reverse switches change their polarity. These movements are all determined by the positioning andexte'nt of thecam regions andth'eir coac'tin'g switches.

Means are provided to limit the extent of the clockwise and counter-clockwise shift to predetermined arcs. To this end, -arm I54 radially extending from the frame 82 terminates in a bearing construction I56 shiftablealong arcuate "slide bar I58. The mo'veme'nt clockwise is against the resistance of spring I60 compressible between a bearing portion I56 and the terminal mount I-52 for the bar I58. "The counter-clockwise shift is against the resistance of spring I64 compressible-between the bearingportion I56 andterminal mount I66 for the bar I58. Upon release'of the foot from the dome '80, the springs return'the mechanism to neutral.

A resilient shock absorber I 68 is 'providedadjacent the forward stop i I10. This-resilientmean's eases the shock as it builds up resistance inthe approach toward the limit I 10 and'in repeated operation of the pedal dur'ing indexing lessens the possibility of the operators foot creeping across the dome even though thedeme' presents a non-skid operating surface.

A resilient take-up may beemploy'ed for the reverse but in that reverse movement is'so seidom used consecutively, a fi-xed 'stop I12 "appears suificient. I

For purposes of stability and eas'e of'inovement, a thrust bearing including a roller track I14 is provided as a support 'fo'rthe frame 82, the flower race or track supporting the bearing being mounted on the bottom '60 of the cup-shaped housing and positione'd to support the frame just insideth'e skirt I36. Th'e-race I14 is horizontally pierced below its top surface by clearways I1 5 for wiring to extend 'therethrough "to the speed switches. The skirt I36 has corresponding-clearways I".

Asshown in Fig. 1 and inF'ig. l0, a plurality of duplicate switch mechanisms may be used connected into acommon circuit.

The mechanism is readily installed into existing apparatus, the hand-piecehook carrying portion of the articulated transmissioni's replaced by a link H6 mounting the housing :34. The housing -may bedispose'd in the pedestal-221i desired, or in some remote place outof the way, with proper conduits therefrom to the vhousing 3'4 and'to the mat.

With the lifting of the operators foot, switch I50 is-efiective to place'a'shunt acrossthe motor armature circuit thus servin as a brake to bring the motor 'to "an instantaneous 'stop preventing any overrun of. the tool after the foot is lifted. This provides the critical control necessary for dentistry.

The mechanism is readily adaptable to variations in installation and in construction and as many units as desired may be placed-adjacent a chair. For example, even asingle unit may be employed with the elimination of switch I52. This would be advantageous inpor'table dental centers.

The camrsfi may be replaced -bymfwhee1- I18 carrying a series of conductor plates I80 insulated from each other, the lines from the resistances 38, 40 and 42 and from the power line H2 are provided with spring finger terminals I82 which may all engage a plate I80 and as the wheel I18 rotates step-by-step, the fingers will spring from one plate to the succeeding plate in sequence to control the speed of the motor.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangements of parts illustrated in the accompanying drawings, since the invention is capable of bein practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not of limitation, and it is not intended to limit the scope of the following claims beyond the requirements of the prior art.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a foot control means for selectively operating a bank of switches, a platform of at least sufiicient lateral extent to support both feet of an operator on even level, a mechanism for selectively operating the switches inset in said platform, a control member for said mechanism comprising a resilient shell providing an axially depressible and rotatable element having at least a portion extending slightly above the surface of said platform to be engaged by an operators foot, and means for detachably connecting and operating said control member to said mechanism responding to the axial depression of said resilient shell to initiate a mechanical operation in connection therewith which is further operable by the rotation thereof.

2. In a foot control for an electric motor, a resilient platform of at least suflicient lateral extent to support both feet of an operator on even level, a cup-shaped member inset into said platform and having a peripheral flange outwardly extending to engage the surface of said platform around said member, means locking said member in the platform and compressing the flange thereinto so that the upper surface of said flange provides substantially a continuation of the supporting area of the platform, a bank of switches in said cup-shaped member, mechanism for operating said switches, a control element for said mechanism comprising a dome-shaped compressible member having its perimeter adjacent the interior of said cup-shaped member and arched outwardly therefrom to provide a foot-engaging area rising slightly above and within the flange, and means operable by compression and rotation of said control element to interlock with and operate said mechanism.

3. In an electric switch mechanism, a housing providing a support, a frame rotatable on said support, spring means operable to position said frame in a neutral position, a control for said frame comprising an element mounted thereby and providing a face to be engaged by an operator to rotate said frame against the resistance of said spring and depress said element toward the frame, additional spring means operable to urge said element longitudinally away from said frame, a member mounted by said frame and radially shiftable by the movement of said element, a

switch operating device, means carried by and operable to interlock said radially shifted member to said switch operating device upon rotation of the control element, and an electric switch operable by said switch operating device.

4. Mechanism for operating an electric switch comprising a housing, a support fixed therein, a. frame rotatable on said support, means coacting between said frame and said support adapted to urge said frame to a neutral position, a control for said frame comprising an element mounted thereby and providing a face to the exterior of the housing to be engaged by an operator to depress said element toward the frame and to rotate said frame, means limiting the rotation of said frame to an are from the neutral position, spring means urging said element from the frame, a member mounted by said frame and shiftable radially outward upon shifting of the element toward the frame and withdrawn through operation of the spring means upon release of said element, a switch operating mechanism, a switch to be operated thereby, and means extending from said radially shiftable member for interlocking said mechanism for operation with said outwardly shifted member upon rotation of said control.

5. Electric switch mechanism embodying a cupshaped housing, a frame rotatable in said housing, a support for said frame, a dome-shaped element having its perimeter mounted on said frame with its central portion outwardly arched toward the open side of said cup-shaped housing and fiexible toward and from the frame, an electric switch in said housing, a rotatable cam for operating said switch, a ratchet and pawl mechanism for imparting a step-by-step rotation of said cam, and means extending between said dome-shaped element and said pawl operable by flexing said element toward the frame and rotating the same, to throw said pawl into engagement with the ratchet, with a subsequent rotation of said cam upon a repeat rotation of said flexed element.

6. In an electric switch mechanism, a rotatable cam, a bank of switches about said cam, said cam adaptable to selectively operate the switches, mechanism for imparting a step-by-step rotation to the cam embodying a ratchet fixed with the cam, a pawl for coacting with said ratchet, a rotary frame mounting said pawl, a support for said frame, means coacting between said pawl and support for urging said pawl toward ratchet engagement upon rotation of said frame, a pad on said frame, means movable upon operation of said pad to engage said pawl and maintain said pawl in ratchet operating position.

7. In a switch mechanism, a rotatable frame, a support for said frame, a cam carried by said frame, an electric switch, said cam adaptable to operate said switch upon rotation of said frame, a pad mounted by said frame, said pad adapted to rotate said frame and to be depressed theretoward, a rotary cam, mechanism operable to rotate said cam step-by-step, a switch operable by said rotary cam, and means operable by said pad to interlock said rotary cam operating mechanism with said frame whereby rotation of said frame may operate both cams and consequently the two switches.

8. In a switch mechanism, two banks of electric switches, a pad for controlling said mechanism in turn selectively operating the two banks of switches, said pad having longitudinal and rotary movements, a rotatable frame for mounting said pad, a support for said frame, a cam carried by said frame for operating the first bank of said switches, means operating the second bank of switches in a predetermined sequence, and means operable by longitudinal and rotary movement of said pad to selectively interlock said frame with the second switch bank operating means whereby both banks of switches may be controlled by rotation of said frame.

9. A switch mechanism embodying a housing, two banks of electric switches in said housing disposed in coaxial relationship about a common center, a frame rotatable about the center, a support for said frame, said frame having a skirt providing cam regions operating the outer bank of switches upon rotation of said frame, a, cam mounted for rotation about the center adapted to operate the inner bank of said switches, a ratchet and pawl drive for said latter cam, a pad carried by said frame, and an element shiftable as to said frame by depression of said pad,

m mi

an electric switch, a cam for operating said switch, a ratchet and pawl mechanism for driving said cam, and interlocking means for said spring shifted element and pawl operable by rotation of the frame by said compressible member.

11. In combination, a dental engine, a circuit for controlling said engine, an articulated support from said engine, and a tool carried by said support; a foot operated switch in said circuit for controlling said circuit to impart selected functions to said engine, and a switch in said circuit mounted on said articulated support embodying an actuator to receive said tool and open said switch, said latter switch rendering said circuit inoperative when supporting said tool.


References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 18,416 Russell et a1. Apr. 12, 1932 508,692 Fiske Nov. 14, 1893 1,538,952 Ram May 26, 1925 1,729,616 Johnson Oct. 1, 1929 1,878,602 Ringbloom Sept. 10, 1932 2,425,985 Blomberg Aug. 19, 1947 2,466,355 Baker Apr. 5, 1949 2,491,748 Martinka Dec. 20, 1949 2,544,491 Davis Mar. 6, 1951 2,560,873 Keckley July 17, 1951

Patent Citations
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US1538952 *Jun 29, 1921May 26, 1925William H Finckel JrTraffic signal
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3253094 *Jul 24, 1963May 24, 1966Chrysler CorpFoot operated dimmer switch with grommet for preventing interference by the floor covering
US3388472 *Oct 1, 1965Jun 18, 1968Price Baker NathanDental drill control
US3963890 *Jun 19, 1973Jun 15, 1976Siemens AktiengesellschaftFoot operated switch assembly with latching structure for operator
US3980849 *Jun 19, 1973Sep 14, 1976Siemens AktiengesellschaftFoot controller switch assembly for dental appliances
US3983344 *Jun 19, 1973Sep 28, 1976Siemens AktiengesellschaftOperated switch controller for dental engine and associated apparatus
US4168707 *Jun 13, 1977Sep 25, 1979Douvas Nicholas GControl apparatus for microsurgical instruments
US5351571 *Sep 11, 1992Oct 4, 1994Johnson Robert EErgonomically symmetric pedal control system
US6013882 *May 9, 1997Jan 11, 2000Dentech Products, Inc.Dental patient's chair
US6608267 *Nov 16, 2001Aug 19, 2003Erbe Elektomedizin GmbhFoot switch including elastic joint for proper positioning of switch component
DE1087755B *Sep 17, 1958Aug 25, 1960Atlas Copco AbDentalgeraet fuer Druckmittelantrieb
EP0008415A1 *Aug 9, 1979Mar 5, 1980Siemens AktiengesellschaftDentist's patient's chair with pivoted backrest
U.S. Classification433/101, 200/86.5, 433/28
International ClassificationA61C1/00
Cooperative ClassificationA61C1/0023
European ClassificationA61C1/00C2A