US2908883A

US2908883A - Rheostat control

Info

Publication number: US2908883A
Application number: US678197A
Authority: US
Inventors: Clifford E Anderson
Original assignee: JOHN ERNEST HILL
Current assignee: JOHN ERNEST HILL
Priority date: 1957-08-14
Filing date: 1957-08-14
Publication date: 1959-10-13
Anticipated expiration: 1976-10-13

Description

Filed Aug. 14, 1957 3 Sheet's-Sheel'I 1 C//ffo/'Q/ f. Ande/:off

INVENTOR. Z MAA) BY 07) g ATTORNEYS' Oct. 13,' 1959 Filed Aug. 14, 1957 C. E. ANDERSON RHEOSTAT CONTROL s Sheets-sheet 2 MMM,

OC- 13, 1959 i c. E. ANDERSON 2,908,883

RHEOSTAT CONTROL Filed Aug. l4, 1957 s sheets-sheet s' (//fjfa/'c/ f. /4//0/2/"50/7 INVENTOR.

.Mmmm B vz) man@ WHW# @wf ATTORNEYS RHEOSTAT CONTROL Clifford E. Anderson, Houston, Tex., assignor to .lohn Ernest Hill, Houston, Tex.

Application August 14, 1957, Serial No. 678,197

16 Claims. (Cl. 338-215) This invention relates to control devices for dental pedal for use with this invention and illustrating one engines and more particularly to control devices which may be operated by movement of a dentists foot.

It is an object of this invention to provide a rheostat control for a dental engine that is simple and compact, and which may be operated by either vertical or lateral movement of a dentists foot.

Another object is to improve the control unit of Hill Patent No. 2,762,891 by placing all of the device within the housing except the foot pedal and toe piece or wing without unduly increasing the size of the housing.

Another object is to provide a rheostat control for a dental engine operated by a vertically movable foot pedal in which there is no tendency to overturn the control in use.

. Another object is to provide a rheostat control for a -dental engine operated by a pivotally mounted vertically movable foot piece for forward and reverse in which the angular movement of the foot pedal is so small that the pedal is never very far from horizontal and there is no tendency to overturn the control.

Another object is to provide a rheostat control for a dental engine operable by both vertically and horizontally movable foot members in which force is applied direct from the foot members to the rheostat contact bar means and very little effort is necessary to operate the control.

Another object is to provide a rheostat control for a dental engine in which separate contact bars are provided for forward and reverse and each bar may be separately operated by either a vertically movable foot pedal or a laterally movable foot piece.

Another object to to provide a dental engine as in the preceding object in which cable means are provided for operating the contact bars with movement of the foot piece and the cables are automatically held taut with movement of the contact bars by either the foot piece or the foot pedal.

Another object is to provide a rheostat control for a dental engine in which separate contact bars provide for y forward and reverse and the bars are positively prevented from both leaving neutral position at the same time.

Another object is to provide a rheostat control for a dental engine in which a foot-operated switch is provided for controlling wash fluid for the dental chair.

Another object is to provide a rheostat control for a dental engine as in the preceding object in which the switch is positioned to be operated simultaneously with the operation of the rheostat by either the foot pedal or the foot piece.

Other objects, features, and advantages of the invention will be apparent from the drawings, the specifications, and the claims.

In the drawings wherein like numerals indicate like 2,908,883 Patented Oct. 13, 1959 2 parts and wherein there is shown by way of illustration several embodiments of this invention:

Fig. l is a View in vertical cross section through a `preferred form of this invention with the section being taken along the lines 1-1 of Fig. 2;

Fig. 2 is a top plan View of the control unit of Fig. 1 ,with the foot pedal and top cover removed, the View being taken along the lines 2 2 of Fig. l;

Fig. 3 is a fragmentary horizontal sectional view taken along the lines 3 3 of Fig. l;

Fig. 4 is a view in vertical cross section through a ymodified form of this invention;

Fig. 5 is a schematic illustration of `a further modified form of this invention;

Fig. 6 is a fragmentary sectional view through a foot form of control switch for a wash Huid valve for a ydental chair;

Fig. 7 is a view of a modified form of a foot piece for use with this invention and illustrating another manner of handling the wash fluid switch;

Fig. 8 is a view along the line 8-8 of Fig. 7;-

Fig. 9 is a fragmentary view of a further modified form a foot piece and illustrating another mounting for the wash fluid valve switch;

Fig. 10 is a fragmentary view of the preferred form of foot piece provided with a wash fluid switch;

Fig. ll is a view along the lines 11-11 of Fig. l0; and

Fig. 12 is a fragmentary sectional View through a foot pedal showing the preferred form of wash fluid switch for use with the foot pedal on top of the rheostat control.

In the preferred form of the invention as illustrated in Figs. 1, 2 and 3, the entire control unit is compactly arranged within a housing indicated generally at 10. Rheostat contact plate means indicated generally at 11 is provided for cooperation with a pair of

contact bars

12 and 13. These bars are individually pivoted within the housing. They are selectively actuated by afoot pedal 14 on top of the housing or by a laterally movable foot piece 15 projecting from the side wall of the housing. As best shown in Fig. 3 the foot piece operates the contact bars through a cable assembly which is held taut at all times to prevent fouling of the cables.

The housing 10 may take any desired form and preferably includes a base 16 and an easily removable cover plate 17.

The rheostat contact plate means 11 is provided by forward contact plate 18 and rear contact plate 19. The contact surface of each plate extends vertically.

Two contact bars, one for forward and one for reverse, are preferably employed to reduce the throw of pedal 14. The forward and

rear contact bars

12 and 13 are pivotally mounted about shaft 21 and urged in an upward direction by spring 22. The contact bars are held in engagement with the rheostat contact plates by an upstanding divider 23 which forms a part of base 16. The contact bars have a sliding engagement with the divider 23.

One means of moving the contact bars from their upper neutral position downwardly along the contact plates is provided by the foot pedal 14. This pedal is pivotally mounted for vertical movement about shaft 24 and for lateral or horizontal movement by the pivotal connection between crank arm 25 and the foot pedal. This connection includes a stud 26 which is threadably secured to the crank arm 25. The stud has a bearing portion 26a about which the foot pedal may rotate.

An operating connection between the foot pedal and contact bars Y*is prefer-ably provided by an actuator 27 which depends from the foot pedal 14. The tops of the contact bars are provided with recesses 28 and 29 which open into the confronting side walls of the two c-ontact bars. The actuator 27 is received within the space provided by these two recesses. Lateral movement of the foot pedal 14 is limited by engagement of the actuator 27 with the side wall of recesses 28 and 29. i

It will be noted that the actuator 27 overlies the two recesses 28 and 29 and the upstanding divider 23. Therefore by lateral movement of the foot pedal 14 the actuator will be` selectively positioned to overlie either

contact bar

12 or 13 and by depressing the pedal the selected contact bar will be moved along a rheostat contact plate to con trol the dental engine.

' As two contact bars are present it is desirable to make certain that at least one of the bars is always in neutral position so that the rheostat ywill not call for both for- Iward and reverse operationof the dental engine. This may be accomplished by providing detent means operable upon movement of one of the contact bars from neutral position to maintain the'other contact bar in neutral position. Such a detent may be provided by a ball 31 carried in a hole 32 extendingL through the spacer 23. The confronting faces of each of the contact bars are provided with dished-in portions indicated at 33 and 34 in dashed outline (Fig. 2) which are in register with bore 32 when both contact bars are in their upper or neutral position. The ball 31 has a slightly larger diameter than the width of the spacer 23. The depth of each dished

portion

33 and 34 is such'as to permit the ball to be just retained within one of the detent portions and the bore .through spacer 23. With this arrangement downward movement of either of the contact bars forces the ball into the dished portion of the other contact bar. So long as one bar is away from neutral position its side wall con fronting the spacer 23 will overlie bore 32 and hold the ball 31 in the dished portion of the other bar and thereby lock the other bar against movement away from the neutral position.

The pivotal mounting for both the foot pedal 14 and the contact bars 12 and 13 is provided by a yoke

assembly including parts

35 and 36. These parts provide journals for

shafts

21 and 24. Part 35 carries a stop 37 and a set screw 38 in crank arm 25 cooperates with this stop to control upward movement of the foot pedal 14.

The rheostat control thus far described in detail will provide complete control of a reversible dental engine by lateral and vertical movement of the foot pedal 14. However, it is frequently necessary. for the dentist to stand at the dental chair. While yworking in the standing position it is preferred to be able to stand with both feet on --the iloor and to operate the rheostat control by lateral movement of one foot using the heel as a pivot. For this purpose the rheostat control is provided with the laterally movable foot piece 15 which also gives complete con- `trol of the two contact bars.

The foot piece 15 is secured to the contact bars by a novel cable means. The cable means includes

cables

39 and 41 secured to the contact bars 12 and 13 respectively. The cables pass downwardly from the bars and over

sheaves

43 and 44 located below the bars. The cables extend from these shea-ves to tackle block 45 which is positioned .between the two cables. After passing over the block 45 cable 39 is secured to a resilient means such as spring 46 anchored to the housing. Likewise cable 41 is vsecured to a resilient means such as spring 47 which is also anchored to the housing.

Cables

39 and 41 are pro- Yvided with stop plates 48 and 49 respectively which engage stops 56) and 51 in the housing to prevent further elongation of the two

springs

46 and 47. These springs are selected to be under tension with the contact bars in 'neutral position. When either of the contact bars is operated by the foot pedal 14, slack is created in the cable attached to the depressed bar and these tension springs take up this slack to avoid fouling of the cables.

The cable arrangement described in detail above provides a fixed track for the cables and the two opposite ends are effectively tied to the housing and contact bars. Therefore any movement of an intermediate section of either of the cables will cause corresponding downward movement of the contact bar to which the cable is secured. To provide for such action lthe footpiece 15 is pivotally mounted at 52 and a vlug 53 is provided on the foot piece at a point spaced from the pivotal mounting 52. This lug 53 is positioned between the

cables

39 and 41 so that movement of foot piece 15 in either .direction from a neutral position will cause movement of an intermediate section of one of

cables

39 or 41 and depress its associated contact bar. Preferably the lug 53 is. provided by a double sheave block with one sheave engaging cable 39 and the other engaging cable 41.

If desired sheaves 54 and 55 may be positioned on the outside of

cables

33 and 41 on opposite sides of pivot 52. As the foot piece 15 is moved from its neutral position the cable being bent by the lug 53 will turn about sheave 54 or 55 as the case may be.

It will be understood that while sheaves are preferred to reduce friction that other means might be used to guide and control the cables.

In operation the rheostat may be controlled with equal facility by either the foot piece 15 or the foot pedal 14. For instance if the foot pedal is moved laterally to the right it will overlie the contact bar 12. Then vertical movement of the foot piece Iwill move contact bar 12 downwardly to obtain the desired speed of the `dental engine. This will tend to slacken cable 39 but this slack will be taken up by the resilient spring 46 and there will be no opportunity for the cable to foul. As the contact bar l2 moves downwardly it will force ball 31 into the dished-in portion 34 of contact bar 13 and will eiectively retain contact bar 13 in neutral position until bar 12 returns to neutral position. The contact bar 13 may be operated in the same manner by moving the foot piece laterally to the left before depressing it.

When standing, the rheostat control may be operated by the toe of the 'dentist by moving foot piece 15 in either direction from the neutral position illustrated. Assuming the vfoot piece to be moved toward the top of the drawing from its position shown in Figs. Zand 3 the lug 53 will bend cable 39 about sheave 54. As the stop parts 48 'and 5 are in engagement the end of cable 39 attached to spring 46 is held stationary. Therefore the contact bar yl2 will be pulled downwardly by cable 39. In so doing it will again move the detent ball 31 into the recess 34 in contact bar 13 and hold contact bar 13 in neutral position until such time as the contact bar-12 is returned to its neutral position.

Referring now tot Fig. v4 there is shown a form of this invention in which the `two contact vbars 12a and 13a `'are mounted on a centrally located pivot 56 and extend in opposite directions from the pivot. The foot pedal indicated generally at 14a is pivoted about a shaft 57 which is positioned approximately above shaft Se.

Actuator means for actuating the Contact bars with movement of foot pedal 14a about its pivot are provided by

actuator arms

53 and 59 which overlie respectively contact bars 12a and 13a. With this form of invention rocking ofthe foot pedal 14a in a clockwise direction operates contact bar 13a and in a eounterclocl-:wise direction operates contact bar 12a. The arrangement and operation of the cooperative foot piece 15 and its cable connection with the contact bars is the same as in the preferred embodiment of this invention with cable 6i) passing over sheave 61 before passing over shea-ve 44.

A still further form of this invention is shown in Fig. 5. In this case only a single Contact bar 63 is provided and is in neutral position when extending horizontally as shown. The forward and reverse systems of the contact plate means would be arranged above and below the contact bar respectively so that the dental engine is operated in `opposite directions by movement of the contact bar 63 in opposite directions from the neutral postition. In this case the foot pedal 14b is provided with an actuator means 64 which is pivotally connected to both the contact bar and the foot pedal so that rocking of the foot pedal about its pivot 65 will cause corresponding movement of the contact bar 63. In this form of the invention the cables 66 and 67 may pass over a sheave positioned approximately at the extremities of movement of foot piece 15 from its neutral position and then be tied `directly to the foot piece. This form of the invention is the least preferred of the three.

In the use of a dental drill driven by a dental engine con- -trolled by the rheostat of this invention it is frequently necessary to wash and cool the field of operation with iiuid. Desirably this should be accomplished by operation of a switch controlled by `the dentists foot which is operating the rheostat control to permit a continued operation. For `this purpose an electrical switch which operates a lluid valve may -be incorporated in the rheostat control in any of the forms illustrated in Figs, 6 through 12.

Referring first to Fig. 6 the foot pedal 14e is provided with a conventional electrical switch 68. The plunger 69 is positioned below an actuator 70 which is held in an inoperative position by resilient means such as the spring 71. Spring 71 causes a bulge in the rubber 72 overlying the foot pedal. It will be apparent that by merely stepping down on the bulge caused by spring 71 that the switch 68 will be actuated to operate a uid valve (not shown) and ood the field of operation with wash uid.

In Figs. 7 and 8 there is shown a fluid wash switch for use with the foot piece 15a. In this instance the pivot for the foot piece 15a is provided by a slotted journal 73 cooperating with the pin 74. Resilient means such as spring 75 urges the foot piece outwardly from the body to the position illustrated in Fig. 8. The switch 68a has its operating plunger 69a in contact with the head of pivot bolt 74 and positioned between the foot piece 15a and lthe pivot 74. Thus by pressing inwardly on the wings extending to either side of foot piece 15a the plunger 69a will be depressed to operate the valve.

Referring now to Fig. 9 the lluid wash switch 68b is shown within the foot piece 15b. The foot piece has an overlying resilient cover 76 which when depressed by the dentists foot `actuates switch 691;.

In Figs. 10 and l1 there is shown the preferred form of wash fluid switch for use with the foot piece. In thisv case the switch 68C is carried on one side of the foot piece C and the plunger 69C extends Ithrough the foot piece 15e. A spring 77 is hooked over the foot piece and overlies the switch plunger 69C. The spring has an outturned flange 78 and the entire foot piece and associated spring and switch Iare covered with resilient material 79. By stepping on the flange 78 as illustrated in Fig. 11 the plunger 69C will `be depressed and the wash iluid valve opened.

Referring to Fig. l2 there is shown the preferred form 'of wash fluid switch for use with the foot pedal. This form is similar to that shown in Fig. 6 except the switch actuator is positioned to the right of the foot pedal and is not under the dentists foot. When it is needed the ldentist merely shifts his heel to the right to step on the switch. The switch actuator 81 may be Secured to the foot pedal 14d in any desired manner (such as on a pivoted arm) for vertical movement to contact the actuator Iswitch 68d will be actuated to provide wash duid at the voperational area.

The foregoing disclosure and description of the in2 vention is illustrative and explanatory thereof and various changes may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

l. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat plate means, a forward contact bar and a reverse contact bar pivotally mounted in the housing for vertical movement along the plate means, a foot pedal pivotally mounted on top of the housing for vertical and lateral movement, and an actuator depending from the pedal `and shiftable between first and second positions with lateral movement of the pedal to engage selectively the contact bars, said actuator moving the engaged contact bar along the plate means `with vertical movement of the foot pedal.

2. The control of claim 1 in combination with a foot operated electrical switch mounted on the pedal for controlling a uid valve whereby a dental drill and wash fluid therefor may be controlled with a single foot.

3. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostate plate means, a forward contact bar and a reverse contact bar pivotally mounted in the housing for vertical movement along the plate means, a foot pedal pivotally mounted on top of the housing for vertical and lateral movement, an actuator depending from the pedal and shiftable between first and second positions with lateral movement of the pedal to engage selectively the contact bars, said actuator moving the engaged contact bar along the plate means with vertical movement of the foot pedal, and detent means operable by movement of one contact bar by the actuator from neutral position to lock the other Contact bar in neutral position.

4. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat contact plate means, a forward contact bar and a rear contact bar pivotally mounted in the housing for vertical movement along the platemeans, a laterally movable foot piece projecting from the side wall of the housing and connected to both contact bars and selectively moving one bar at a time along the contact plate means with movement of the foot piece on either side of neutral position, a foot pedal pivotally mounted on top of the housing for vertical movement, and actuator means extending between the bars and pedal and moving one of the bars along the plate means with selective vertical movement of the pedal. l

5. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat contact plate means, a forward contact bar and a rear contact bar pivotally mounted in the housing for vertical movement along the plate means, a laterally movable foot piece projecting from the side wall of the housing and connected to both contact bars and selectively moving one bar at a `time along `the Contact plate means with movement of the foot piece on either side of neutral position, a foot pedal pivotally mounted on top of the housing for vertical movement, actuator means extending between the bars and pedal and moving one of the bars along the plate means with selective vertical movement of the pedal, and detent means operable by movement of one contact bar by the actuator from neutral position to Ilock the other contact bar in neutral position.

6. A rheostat control for a dental engine comprising, a housing having mounted therein f orward and reverse rheostat contact plates, a pair of rheostat contact bars pivoted in the housing, a laterally movable foot piece projecting from the side wall of the housing and connected to both contact bars and selectively moving one bar at a time along a contact plate with movement of the foot piece on either side of a neutral position, a foot pedal pivotally mounted on top of the housing for vertical and .lateral movement, an actuator depending from the pedal and shiftable laterally between first and second positions to selectively engage the contact bars, said actuator moving the engaged contact bar along a contact plate with verticl movement of the foot pedal.

y 7. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse Vrheostat plate means, a pair of rheostat contact bars 4pivoted inthe housing, a foot pedal pivotally mounted on top of the housing for vertical movement, actuator means extending between the bars and pedal and moving one f the bars along the plate means with selective vertical movement of the pedal, a laterally movable foot piece projecting from the side wall of the housing, and cable means connecting the foot piece with the contact bars 4and effecting selective movement of one bar at a time v along the contact plate means with movement of the foot piece on either side of a neutralposition, said cable connecting means maintaining the cables taut while the contact bars are operated by the foot pedal.

8. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse lrheostat plate means, a pair of rheostat contact bars pivoted in the housing, a foot pedal pivotally mounted on .top of the housing for vertical movement, actuator means extending between the bars and pedal and moving one of the bars along the plate means with selective vertical movement of the pedal, a laterally movable foot piece projecting from the side wall of the housing, cable means connecting the foot piece with the contact bars and effecting selective movement of one bar at a time along the contact plate means with movement of the foot piece on either side of a neutral position, said cable connecting means maintaining the cables taut while the contact bars are operated by the foot pedal, and detent means operable by movement of one contact bar by the actuator from neutral position to lock the other contact bar in neutral position.

9. The control of claim 8 in combination with a foot operated electrical switch mounted on one of the pedal and foot piece for controlling a uid valve whereby a dental drill and wash uid therefor may be controlled with a single foot.

10. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat contact plates, a pair of rheostat Contact bars pivoted in the housing, a foot pedal pivotally mounted on top of the housing for vertical and lateral movement, an actuator depending from the pedal and shiftable laterally between iirst and second positions to selectively lengage the contact bars, said actuator moving the engaged contact bar along its associated plate with vertical movement of the foot pedal, a laterally movable foot piece projecting from the side wall of the housing and cable means connecting the foot piece with the contact t bars and effecting selective movement of one bar ata time along its contact plate with movement of the foot piece on each side of a neutral posi-tion, said cable connecting means maintaining the cables taut While the contact bars are operated by the foot pedal.

ll. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat contact plates, a pair of rheostat contact bars pivoted in the housing, a laterally movable foot piece projecting from the housing and pivotally mounted therein, a lug on the foot piece spaced from said pivotal mounting, cables extending between the contact bars and tension resilient means mounted in the housing, said resilient means maintaining the cables taut, and stop means preventing elongation of said resilient means, said 4cables passing over opposite sides of the lug whereby .movement of the foot piece in either direction from a neutral position will move one of the cables laterally and cause movement of a contact bar.

l2. A rheostat control for a dental engine comprising,

a housing having mounted therein forward and reverse rheostat contact plates, a pair of rheostat contact bars pivoted in the housing, a laterally movable foot piece projecting from the housing and pivotally mounted therein, a lug on the foot piece spaced from said pivotal mounting'cables extending between the contact bars and tension resilient means mounted in the housing, said resilient means maintaining the cables taut, stop means preventing elongation of said resilient means, said cables passing over opposite sides of the lug whereby movement of the foot piece in either direction from a neutral position will move one of the cables laterally and cause movement of a contact bar, and detent means operable by movement of one contact bar by the actuator from neutral position to lock the other contact bar in neutral position.

13. A rheostat control for a dental engine comprising, a housing adapted to rest on the floor beside a dental chair and having mounted therein forward and reverse rheostat contact plate means, a forward contact bar and a reverse contact bar pivotally mounted in the housing for vertical movement along the plate means, a foot pedal pivotally mounted on top of the housing for vertical and lateral movement, an actuator depending from the pedal and shiftable between first and second positions with lateral movement of the pedal to engage selectively the contact bars, said actuator moving the engaged contact bar along the plate means with vertical movement of the foot pedal, a laterally movable foot piece projecting from the housing and pivotally mounted therein, a lug on the foot piece spaced from said pivotal mounting, cables extending between the contact bars and tension springs mounted in the housing, and stop means preventing elongation of said springs, said cables passing over opposite sides of the lug whereby movement of the foot piece in either direction from a neutral position will move one of the cables laterally and cause movement of the contact bar, said tension springs maintaining the cables taut while the contact bars are operated by the foot pedal.

14. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat contact plate means, a forward contact bar and a rear contact bar pivotally mounted inthe housing for vertical movement along the plate means, a laterally movable foot piece projecting from the side wall of the housing and connected to both contact bars and selectively moving one bar at a time along the contact plate means with movement of the foot piece on either side of neutral position, a foot pedal pivotally mounted on top of Vthe housing for vertical movement, actuator means extending between the bars and pedal and moving one of the bars along the plate means with selective vertical movement tof the pedal, and a foot operated electrical switch `.mounted on one of the pedal and foot piece for controlling a huid valve whereby a dental drill and wash fluid therefor may be controlled with a single foot.

l5. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat Contact plates, a pair of rheostat contact bars pivoted in the housing, a laterally movable foot piece projecting from the housing and pivotally mounted therein, a lug on the foot piece spaced from said pivotal mounting, cables extending between the contact bars and tension resilient means mounted in the housing, said resilient means maintaining the cables taut, stop means preventing elongation of said resilient means, said cables passing over opposite sides of the lug whereby movement of the foot piece in either direction from a neutral position will move one of the cables laterally and cause movement of a contact bar, and a foot operated electrical switch mounted on the foot piece for controlling a fluid valve whereby a dental drill and wash fluid therefor may be controlled with a single foot.

16. A rheostat control for a dental engine comprising, a housing having mounted therein forward and reverse rheostat contact plate means, contact bar means pivotally mounted in the housing for movement in a vertical plane along the plate means, a foot pedal pivotally mounted on top of the housing for movement in a vertical plane, actuator means extending between the bar means and the pedal and moving the bar means along the plate means with vertical movement of the pedal, and a foot operated electrical switch mounted on the pedal for controlling a fluid valve whereby a dental drill and wash uid therefor may be controlled with a single foot.

References Cited in the ile of this patent UNITED STATES PATENTS Hammond Aug. 30, Flegel June 29, Aiala Dec. 6, Wyer July 3, Eisenberg Feb. 1, Hill et al. Sept. 11,