US3514153A - Dental chair control - Google Patents

Description

y 1970 J. A. MAURER ETAL 3,514,153

DENTAL CHAIR CONTROL 4 Sheets-Sheet 1 Filed June 3, 1968 INVENTORS. John/A Mall/Per,

VLci'or R. Fe Ll/ Mil/bur L. E6

AT TOJ ZNEYS May 1970 J. A. MAURER ETAL 3,514,153

DENTAL CHAIR CONTROL 4 Sheets-Sheet 1:

Filed June 3. 1968 28011 51 "him! INVENTORS.

VIIGThI'RF?! WzlburL E.

ATTORNEYS L John 44 Mural y 25, 1970 J. A. MAURER ETAL 3,514,153

DENTAL CHAIR CONTROL Filed June 5. 1968 4 Sheets-Sheet 3 BACK CYLINDER WIPER DRAIN TUBE SEAT UP SOL SEAT DOWN SOL BACK UP SOL SEAT CYL

JACK UP SOL CHECK VALVE INTAKE SCREEN INVENTORS. John/A. Man/m1", VicZbrRFeIyusopA- 44 WiLbzuLEywn/smhed F 19 57 WW 12 ATTORNEYS May 26, 1970 BACK I53 Filed June 5. 1968 J. A. MAURER ETAL DENTAL CHAIR CONTROL SEAT SEAT SEAT U P DOWN 2 IMUTOR STARHNG I RELAY ATTORNEYS INVENTORS Jvhn/A Ma/z I/rer, ViolorRFmyu WiLbzwLBpen/s 9312mm 8 W BACK UP 501; (Jued/ United States Patent 3,514,153 DENTAL CHAIR CONTROL John A. Maurer, Victor R. Ferguson, and Wilbur L.

Espenschied, Canton, Ohio, assignors to The Weber Dental Manufacturing Company, Canton, Ohio, a corporation of Ohio Filed June 3, 1968, Ser. No. 734,113 Int. Cl. A47c 3/30 US. Cl. 297-71 9 Claims ABSTRACT OF THE DISCLOSURE Control means for a dental chair having a hydraulic cylinder operated jack, a seat pivotally connected to the upper end of the jack, a seat back pivotally connected to the seat, hydraulic cylinder means for tilting the seat up and down and hydraulic cylinder means for raising and lowering the seat back.

A motor driven pump draws oil from an oil sump and pumps it to the various cylinders through a hydraulic circuit. A plurality of solenoid valves selectively control the flow of oil to and from the several cylinders.

The motor and solenoids are located in an electrical circuit containing a motor relay and a solenoid relay controlled by a thermal relay. A set of electrical switches on each side of the seat back independently controls the motor and the solenoid switches for up and down movement of the jack, up and down movement of the seat back, and up and down tilting movement of the chair seat.

A return switch on each side of the seat back simultaneously controls the motor and all of the proper solenoid valves, through the thermal relay, to move the chair from a jack up, seat back down and seat titlted up position, to a jack down, seat back up and seat tilted down or level position.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to control means for a dental chair having a jack for raising and lowering the chair seat, a seat pivotally mounted at its rear end upon a seat saddle on the top of the jack, and a seat back pivotally mounted upon the rear end of the seat frame.

The control to which the invention pertains includes electrical means actuated by two sets of four rocker switches which may be operated from either a left or right position. These switches are of a conventional type which may be rocked in either of two opposite direc tions to make contact. The switches are momentary in action so that they return to the normal off position when released.

The jack is raised and lowered by a hydraulic cylinder, the chair seat is titled up or down to level or nomal position by a second hydraulic cylinder and the seat back is tilted down or up by a third hydraulic cylinder.

A motordriven pump draws oil from a sump at the bottom of the jack and selectively delivers the oil to the cylinders or returns it to the sump through the operation of a plurality of electromagnetic solenoid valves which are selectively individually actuated by certain ones of the switches.

A return switch is provided for simultaneously operating the motor-driven pump and the proper combination of solenoid valves for raising the seat back from the lowered position to the up position, and at the same time lowering the tilted seat to normal or level position and simultaneously lowering the jack to the normal or lowered position.

'ice

The motor and solenoids are located in an electrical circuit in which is located a motor relay and a solenoid relay controlled by a thermal relay. The return switch on each side of the chair controls the motor and the proper solenoid valves through the thermal relay.

Description of the prior art Although it is known that dental chairs have been made with hydraulic cylinder operated means for raising and lowering the jack, tilting the seat and raising and lowering the seat jack, through electrically controlled means it is not known that anyone has previously produced control means such as that disclosed in the present application and especially a single return switch for operating means for simultaneously raising the seat back, lowering the seat from tilted to level position and lowering the jack from raised to lowered position.

SUMMARY OF THE INVENTION In general terms, the invention may be briefly described as comprising control means for a dental chair which is raised and lowered by a hydraulic cylinder operated jack. A seat saddle is fixed to the upper end of the jack, and a seat frame is pivotally connected at its rear end to the seat saddle and adapted to have its forward end titlted upward away from the seat saddle by means of a hydraulic cylinder.

A seat back frame is pivotally connected at its lower end to the rear end of the seat frame and adapted to be lowered and raised relative to the seat frame by a third hydraulic cylinder.

A hydraulic circuit is provided for the cylinders including a sump at the bottom of the jack, a motor-driven pump receiving oil from the sump, and a series of tubular conduits leading from the pump to the several cylinders with return lines from the cylinders to the sump.

In the embodiment disclosed the jack and the seat back are each operated by a single action hydraulic cylinder while the seat tilting mechanism is operated by a doubleacting cylinder. The control means includes eight solenoid valves located in the hydraulic circuit. One of the solenoid valves is located between the pump and the inlet to the seat back cylinder and is hereinafter referred to as the back up solenoid valve and a second solenoid valve is located between the back raising cylinder and the oil sump and is hereinafter referred to as the back down solenoid.

Four of the solenoid valves are used in connection with the seat tilting mechanism. A seat up solenoid valve is located between the pump and one end of the seat tilting cylinder, and a seat up exhaust solenoid valve is located between the other end of this cylinder and the oil sump. A seat down solenoid valve is located between the last-named end of the seat tilting cylinder and the pump and a seat down exhaust" solenoid valve is located between the first mentioned end of this cylinder and the oil sump.

A jack up solenoid valve is located between the pump and the inlet end of the jack cylinder and a jack down solenoid valve is located between the jack cylinder and the oil sump.

A set of four electric rocker switches is provided in an electrical circuit in which the pump motor is located. In order that these switches may be easily operated by either a lefthanded or right-handed dentist, there are duplicate sets of the four switches on each side of the chair so that they may be operated from either a left or right position. Each of these switches is a rocker switch which may be depressed in either of two opposite directions to make contact, and all of these switches are momentary in action; that is, the switches return to normal or oil position when released.

One of these electric switches, the top switch in the embodiment disclosed, controls the up and down movement of the chair seat back. The up position of this switch controls the back up solenoid valve and at the same time operates the motor driven pump to produce hydraulic pressure to raise the seat back. The down position of this switch operates the back down solenoid valve which allows the oil stored in the back raising cylinder to drain to the oil sump, whereby the seat back will be lowered by gravity to substantially horizontal position.

The second or seat tilt switch operates the chair seat tilting mechanism. The up position of this switch starts the motor driven pump and simultaneously operates the seat up solenoid valve and the seat up exhaust solenoid valve to raise the chair seat to a tilted position. The pump, of course, provides hydraulic pressure to the raising end of the cylinder while the seat up exhaust solenoid valve is opened to exhaust oil from the other end of the cylinder to the oil sump.

The down position of this switch operates the motor driven pump and simultaneously operates the seat down solenoid valve and the seat down exhaust solenoid valve so that the pump furnishes hydraulic pressure to the lowering end of the cylinder while the seat down exhaust solenoid valve is opened to exhaust oil from the opposite end of the cylinder to the sump, lowering the seat to normal or substantially horizontal position.

The third electric switch operates the jack up or down. The up position of this switch starts the motor driven pump and operates the jack up solenoid valve between the pump and the inlet to the cylinder to raise the jack by hydraulic pressure.

The down position of this switch operates the jack down solenoid valve between the cylinder and the oil sump, allowing the stored oil in the jack cylinder to return to the oil sump and permitting the entire upper structure to lower by gravity.

The fourth and last electric switch in each group is a return switch and may be momentarily rocked in either direction to return all parts of the chair to normal position. The thermal delay relay allows this operation to be controlled for a preset predetermined time only.

Assuming that the jack is raised, the chair seat tilted and the seat back lowered, when the return switch button is depressed in either direction all three relays, namely, the thermal relay, the motor relay and the solenoid relay are energized.

The solenoid relay operates the seat down solenoid valve and the seat down exhaust solenoid valve and simultaneously furnishes electrical voltage to the thermal delay heater so that the return switch does not require sustained depression. Simultaneously the back up solenoid valve is operated, the jack down solenoid valve is operated and at the same time the motor driven pump is energized to provide hydraulic pressure to raise the seat back and level the chair seat, and the jack is allowed to lower to normal position by gravity, by exhausting oil stored in the jack cylinder to the oil sump. The thermal relay maintains a closed circuit of its contacts until warping action of the bimetallic strip opens its contacts. All relays then thus return to normal position.

A primary object of the invention is to provide a dental chair control having independent electric switch means for controlling the up and down movement of the chair seat back; independent electric switch means for controlling tilting of the chair seat upward and back to level position; and independent electric switch means for controlling up and down movement of the chair jack.

Another object of the invention is to provide a single electric return switch means for simultaneously controlling raising of the seat back, tilting of the seat downward to level position and lowering of the seat to normal position.

A further object of the invention is to provide such control means including cylinder means for raising and lowering the seat back, cylinder means for tilting the seat, cylinder means for raising and lowering the jack, a motor driven pump for furnishing hydraulic pressure to the cylinders, a hydraulic circuit connecting the pump to the cylinders with a return line from the cylinders to an oil sump, and solenoid valves in the hydraulic circuit, and an electric circuit in which the motor and solenoids are located with separate electric switch means for independently energizing the solenoids for each cylinder and a single electric return switch means for simultaneously energizing certain of the solenoids to return the chair seat back, chair seat and jack to normal positions.

A still further object of the invention is to provide such a control in which the electric circuit includes a thermal relay, a solenoid relay and a motor relay, the thermal relay having a bimetallic strip which controls the circuit to the solenoid relay and the motor relay.

These and other objects, apparent from the drawings and following description, may be attained, the above described difiiculties overcome and the advantages and results obtained, by the apparatus, construction, arrangement and combinations, subcombinations and parts which comprise the present invention, a preferred embodiment of which, illustrative of the best mode in which applicants have contemplated applying the principle, being set forth in detail in the following description and illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a chair in normal position, provided with the control to which the invention pertains;

FIG. 2 is a side elevation of the chair in raised position with the back lowered and the seat tilted;

FIG. 3 is a larger scale top plan view of the seat frame with the upholstery and wiring removed;

FIG. 4 is a longitudinal sectional view through the seat frame showing the seat tilting cylinder in elevation, taken on the line 44, FIG. 3;

FIG. 5 is a longitudinal sectional view through the seat frame and back frame showing the seat back cylinder in elevation, taken on the line 55, FIG. 3;

FIG. 6 is an enlarged transverse sectional view taken on the line 66, FIG. 3;

FIG. 7 is a fragmentary longitudinal section on the line 7-7, FIG. 3;

FIG. 8 is a diagrammatic view of one of the rocker switches;

FIG. 9 is a diagrammatic view of the hydraulic system; and

FIG. 10 is a wiring diagram.

Referring now more particularly to the embodiment of the invention illustrated, a representative dental chair construction is indicated generally at 20 in FIGS. 1 and 2, and includes a chair assembly 21 and jack assembly 22. The chair assembly includes a chair seat 23, and a seat back 24 to which may be connected a detachable head rest 25. The jack assembly may be of any conventional construction, such as that shown in Maurer et al. Pat. 3,044,802 issued Oct. 17, 1961. As in usual practice the jack assembly may be rotatably mounted upon a floor plate 26.

The jack assembly includes a stationary upright piston assembly 27 telescoped within the vertically reciprocal fluid cylinder assembly 28. As disclosed in said Pat. No. 3,004,802, the jack cylinder assembly vertically moves the inner jack section 29 (FIG. 2) and the intermediate jack section 30. Upon the upper end of the inner jack section 29 is fixed a seat saddle 31 to which is pivotally mounted the rear end portion of the seat frame 32 as indicated at 33 in FIG. 4.

A double acting fluid cylinder 34 (FIGS. 4 and 9) is pivotally connected as at 35 to the seat saddle 31, and the piston rod 36 thereof is pivotally connected as at 37 to the seat frame 32 for tilting the seat upward as indicated in FIG. 2 and down to level position as shown in FIG. 1.

The seat back cylinder 38 (FIGS. 5 and 9) is pivotally connected at 39 to the seat frame 32 and the piston rod 40 thereof is pivotally connected at 41 to the seat back frame 42 (FIG. 5) for raising the seat back 24 to the upright position of FIG. 1 and for lowering it to the sub stantially horizontal position of FIG. 2.

The stationary piston 27 of the jack is hollow as best shown in FIG. 9 and the lower end thereof is fixed within the jack base 43 which is mounted in the oil sump 44. A motor-driven pump 45 (FIG. 9) has an inlet pipe 46 connected to an intake screen 47 within the oil sump. This pump furnishes hydraulic pressure for the jack cylinder 28, the seat tilt cylinder 34 and the seat back cylinder 38.

FIG. 9 is a hydraulic diagram showing the connection of the pump 45 and oil sump 44 to the three cylinders through a plurality of solenoid valves. The outlet pipe 48 from the pump 45 leads through a pressure relief valve 49 and check valve 50 to a Y-coupling 51. One arm 52 of the Y-coupling is connected by tube 53 to the solenoid valve 54 actuated by the jack up solenoid 54". Tube 56 leads from the jack up solenoid valve 54 through the jack raising check valve 57 to the inlet opening 58 in the jack base 43.

The other arm 59 of the Y 51 is connected by tube 60 with the inlet manifold 61. The inlet manifold 61 is connected to the inlet sides of the back up solenoid valve 62, seat down solenoid valve 63 and seat up solenoid valve 64. The back up solenoid valve 62 is connected by tube 65 with a T-coupling 66, one arm 67 of which is connected by tube 68 with the chair back cylinder 38. The other arm 69 of the T coupling 66 is connected by tube 70 with the back down solenoid valve 71 which also communicates with the exhaust manifold 72.

A drain pipe 73 leads from the exhaust manifold 72 to the oil sump 44. A T-coupling 74 is connected to the discharge side of the seat down solenoid valve 63 and a pipe 75 leads from one side of the head of the T-coupling 74 to one end of the double-acting seat tilt cylinder 34. A pipe 76 leads from the other side of the head of the T-coupling 74 to the seat up exhaust solenoid valve 77 which also discharges into the exhaust manifold 72.

A pipe 78 connects the seat up solenoid valve 64 with a T-coupling 79, one side of which is connected by pipe 80 to the other end of the seat tilt cylinder 34. Pipe 81 connects the other side of the T-coupling 79 to the seat down exhaust solenoid valve 82 which discharges into the exhaust manifold 72. A wiper drain tube 83 connects the upper end of the seat back cylinder 38 to the oil sump 44 for draining from the cylinder 38 any oil which may leak past the piston 84 thereof.

The inlet opening 58 in the jack base communicates with the horizontal passage 85 which connects at its inner end to the lower end of the hollow jack cylinder piston 27 and at its outer end to the discharge pipe 86 leading to the jack down solenoid valve 87 Drain pipe 88 leads from the jack down solenoid valve 87 to the oil sump 44, through a cushion valve 89.

A pump bleed oft drain tube 90 leads from one side of the motor-driven pump 45 to the oil sump 44, and a pump drain pipe 90' leads from the top of the pump to the oil sump for draining any seepage of oil from the pump.

FIG. 10 is an electric wiring diagram showing the electrical means for energizing the pump motor and the various solenoids for operating the several hydraulic cylinders that control the raising and lowering of the jack, the tilting of the chair seat and the raising and lowering of the seat back.

A line cable is shown at 91 containing a green wire 92 that is grounded, a black wire 93 connected to terminal 6 of the motor starting relay 94, and a white wire 95 connected to terminal 5 of the motor starting relay 94. A capacitor 96 is connected to terminal 1 of the motor starting relay '94 by wire 97 and is connected to terminal 4 of said relay by wire 98. Red wire 99 leads from terminal 2 of the relay to the pump motor, yellow wire 100 leads from terminal 5 of the relay to the motor, and blue wire 101 leads from terminal 4 of the relay to the motor.

A white wire 102 leads from the terminal 5 of the motor starting relay to terminal 5 of the terminal block 103. Wire 104 leads from terminal 5 of terminal block 103 to the jack down solenoid 87, and wire 105 leads from the same terminal 5 to jack up solenoid 54. White wire 106 leads from terminal 5 of the terminal block 103 through the connector plug 107 to terminal 5 of the terminal block 108. Orange wire 109 leads from terminal 8 of terminal block 103 through the connector plug 107 to terminal 8 of terminal block 108. Blue wire 110 leads from terminal 7 of terminal block 103 through connector plug 107 to terminal 7 of terminal block 108. Black wire 111 leads from terminal 6 of the motor starting relay through the connector plug 107 to terminal 6 of the terminal block 108. Red wire 112 leads from terminal 4 of the motor starting relay 94 through the connector plug 107 to terminal 4 on the terminal block 108.

A wire 113 leads from terminal 5 of terminal block 108 to the seat down exhaust solenoid 82, the seat up exhaust solenoid 77, the back down solenoid 71, the seat up solenoid 64, the seat down solenoid 63, and the back up solenoid 62, and a wire 114 leads from terminal 10 of the terminal block 108 to the back up solenoid 62.

Black wire 115 leads from the seat down exhaust solenoid 82 to the terminal 13 of the terminal block 108 and wire 116 leads therefrom to the seat down solenoid 63. Blue wire 117 leads from terminal 11 of the terminal block 108 to the back down solenoid 71. Wire 118 leads from terminal 12 of the terminal block 108 to the seat up exhaust solenoid 77 and wire 119 leads from the same terminal to the seat up" solenoid 64. White wire 120 leads from terminal 14 of the terminal block 108 to terminal 14 of the solenoid relay 121.

Red wire 122 leads from terminal 4 of the terminal block 108 through the flexible cable 123 to terminal 4 of the terminal block 124. Red wire 125 also leads from terminal 4 of terminal block 108 to terminal 4 of the motor relay 126. Black wire 127 leads from terminal 6 of terminal block 108 through cable 123 to terminal 6 of terminal block 124. Another black wire 128 leads from the same terminal 6 of terminal block 108 to terminal 6 of solenoid relay 121 and through wire 129 to terminal 6 of motor relay 126.

Blue wire 130 leads from terminal 7 of terminal block 108 through flexible cable 123 to terminal 7 of terminal block 124. Orange wire 131 leads from terminal 8 of terminal block 108 through flexible cable 123 to terminal 8 of terminal block 124. A second orange wire 132 leads from the same terminal 8 of terminal block 108 to terminal 8 of solenoid relay 121. White wire 133 leads from terminal 10 of terminal block 108 through flexible cable 123 to terminal 10 of terminal block 124. A second white wire 134 leads from the same terminal 10 of terminal block 108 to terminal 10 of the solenoid relay 121. White Wire 1335 leads from terminal 5 of terminal block 108 to terminal 5 of the thermal relay 136. Another wire 137 leads from terminal 5 of terminal block 108 to terminal 5 of solenoid relay 121, and wire 137 leads therefrom to the terminal 5 of the motor relay 126.

A blue wire 138 leads from terminal 11 of terminal block 108 through flexible cable 139 to terminal 11 of terminal block 124. Black wire 140 leads from terminal 12 of terminal block 108 through flexible cable 139 to terminal 12 of terminal block 124. Another wire 141 leads from the same terminal 12 of terminal block 108 to terminal 12 of the motor relay 126. Orange wire 142 leads from terminal 13 of terminal block 108 through flexible cable 139 to terminal 13 of terminal block 124.

Red wire 143 leads from terminal 14 of terminal block 108 through flexible cable 139 to terminal 14 of terminal block 124 and white wire 144 leads from the same terminal 14 of terminal block 108 through flexible cable 139 to terminal 15 of terminal block 124.

Wire 145 leads from terminal 15 of terminal block 108 to terminal 15 of the solenoid relay 121. Another wire 146 leads from the same terminal 15 of terminal block 108 to terminal 15 of the motor relay 126. Wire 147 leads from terminal 14 of terminal block 108 to terminal 14 of thermal relay 136. Wire 148 leads from terminal 15 of terminal block 108 to terminal 15 of thermal relay 136, and then through wire 148' to the bimetallic strip 136a of the thermal relay 136.

Duplicate sets of four electric rocker switches, indicated generally at 149, are located on opposite sides of the chair back (FIGS. 1 and 2) and are located in the electric circuit as best shown in FIG. 10. These rocker switches actuate the pump motor and the solenoid valves which control the several hydraulic cylinders.

One of these rocker switches is shown diagrammatically in FIG. 8 and comprises generally a shallow V-shaped insulation button 150 centrally pivoted as at 151 and provided with spring means 152 for normally holding it in open or ofi? position. Contacts, as indicated at 153, at opposite ends of the rocker button 150 are adapted to alternately make contact with stationary contacts 154 when the rocker button 150 is manually depressed in either direction.

As shown in FIG. 10, a wire 155 leads from the terminal 6 upon terminal block 124 to each of the contacts 153 of each rocker switch. As indicated on FIG. 10, depression of the rocker buttons 150 to the left closes the circuit to the proper solenoids for up movement of the cylinders controlled thereby while depression of the rocker buttons to the right closes the circuit to the proper solenoids for down movement of said cylinders.

A wire 156 leads from the terminal 4 of the terminal block 124 to the stationary contact 4 on the down side of the seat tilt switch in the lefthand group, and a similar wire 157 leads from the terminal 4 of the terminal block 124 to the corresponding stationary contact 4 on the down side of the seat tilt switch in the righthand group. A wire 158 leads from the terminal 7 on the terminal block 124 to the stationary contact 7 on the up side of the jack switch in the lefthand group and a similar wire 159 leads from the terminal 7 of terminal block 124 to the corresponding stationary contact 7 on the up side of the jack switch in the righthand group. The stationary contact 4 on the down side of each seat tilt switch is connected by a wire 160 with the corresponding stationary contact on the up side of the same seat tilt switch, and this latter contact is connected by a series of wires 1-61 with one of the stationary contacts on the up side of each of the back switch, seat tilt switch and jack switch of that group.

A wire 162 connects the terminal 8 of terminal block 124 to the stationary contact 8 on the down side of the jack switch in the lefthand group and a similar wire 163 connects the terminal 8 of terminal block 124 to the stationary contact 8 on the down side of the jack switch in the righthand group: A wire 164 connects the terminal 10 of terminal block 124 to the stationary contact 10 on the up side of the back switch in the lefthand group, and a similar wire 165 connects the terminal 10 on terminal block 124 to the stationary contact 10 on the up side of the back switch in the righthand group.

A wire 166 leads from the terminal 11 on terminal block 124 to the stationary contact 11 on the down side of the back switch in the lefthand group, and a similar wire 167 leads from the terminal 11 of terminal block 124 to the stationary contact 11 on the down side of the back switch in the righthand group. A wire 168 leads from the terminal 12 of terminal block 124 to the stationary contact 12 on the down side of the seat tilt switch in the lefthand group, and a similar wire 169 8 leads from the terminal 12 on terminal block 124 to the stationary terminal 12 on the down side of the seat tilt switch in the righthand group.

A wire 170 leads from the terminal 13 of terminal block 124 to the stationary contact 13 on the up side of the seat tilt switch in the lefthand group, and a similar wire 171 leads from the terminal 13 of terminal block 124 to the stationary terminal 13 on the up side of the seat tilt switch in the righthand group.

A wire 172 leads from the terminal 14 on terminal block 124 to the stationary contact 14 on the down side of the return switch in the lefthand group, and a similar wire 173 leads from the terminal 14 on terminal block 124 to the stationary contact 14 on the down side of the return switch in the righthand group.

Wire 174 leads from terminal 15 of terminal block 124 to the stationary contact 15 on the up side of the return switch in the lefthand group and a similar wire 175 leads from terminal 15 on terminal block 124 to the stationary contact 15 on the up side of the return switch in the righthand group.

OPERATION Assuming the chair to be in the normal position, as shown in FIG. 1, with the seat 23 tilted down to level position, the seat back 24 in the raised position and the jack in down position so that the seat is at its lowermost position substantially resting upon the jack assembly 22, the seat back 24 may be lowered, the seat tilted upward and the jack raised to the position of FIG. 2 by pressing the rocker buttons of the back switch, seat tilt switch and jack switch of either the lefthand or righthand group in the proper direction.

To lower the back to the position of FIG. 2, the rocker button 150- of the back switch, in either the lefthand or righthand group is moved to actuate the switch to down position, closing the circuit to the back down solenoid 71 so that the back down solenoid valve is opened permitting oil stored in the lower or righthand end of the back cylinder 38 to drain through the tube 68, T 66, tube 70, back down solenoid valve 71, exhaust manifold 72 and drain pipe 73 to the oil sump 44 (FIG. 9). The back 24 will thus be lowered to the position shown in FIG. 2 by gravity, the weight of the patient in the chair, added to the weight of the back 24, causing the same to be lowered quite easily.

To tilt the front end of the seat 23 upward to the position shown in FIG. 2, the rocker button of the seat tilt switch of either group is moved to actuate the switch to down side, closing the circuit to the motor pump 45 and simultaneously closing the circuit to the seat up solenoid 64 and seat up exhaust solenoid 77, while fluid pressure from the pump 45 passes up through the pipe 48, pressure relief valve 49, check valve 50, T 51, pipe 60, inlet manifold 61, seat up solenoid valve 64, pipe 78, T 79 and pipe 80 to the lower end of the seat tilt cylinder 34, raising the piston 34a therein and, through the piston rod 36, tilting the forward end of the seat frame 32 upward (FIG. 4) pivoting upon the pivot point 43 at the rear end of the seat saddle 31. Oil stored in the cylinder 34, above the piston 38, will be exhausted through the pipe 75, the open seat up exhaust solenoid valve 77 to the exhaust manifold 72 and then through the drain pipe 73 to the oil sump 44.

To operate the jack in order to raise the entire chair to the position shown in FIG. 2, the rocker button of the jack switch, in either group, is moved to actuate the switch to up position simultaneously closing the circuit to the pump motor 45 and to the jack up solenoid valve 54'. Again, oil pressure from the pump passes up through the pipe 48, pressure relief valve 49, check valve 50, T 51, and pipe 53 to the open jack up solenoid valve 54, then through the pipe 56, jack raising check valve 57, inlet 58 in the jack base 43, and then up through the stationary piston 27, raising the cylinder tube 28 as disclosed in said Maurer et al. Pat. No. 3,004,802, raising the inner jack section 29 and intermediate jack section 30 and thereby raising the entire chair structure to the position shown in FIG. 2.

With the chair in the position shown in FIG. 2 it may be quickly and easily returned to the normal position of FIG. 1 by pressing the rocker button of the return switch on either side. This energizes the thermal relay 136, the motor relay 126, and the solenoid relay 121. The solenoid relay 121 operates the seat down solenoid 63 and the seat down exhaust solenoid '82. Simultaneously, it furnishes electrical voltage to the thermal relay heater so that the return switch rocker button does not require sustained depression but may be immediately released. Simultaneously the pump motor 45 is energized to provide hydraulic pressure to raise the seat back and level the tilt of the seat. Simultaneously the jack down solenoid 87 is energized allowing the jack to lower to normal position by exhausting oil stored in the cylinder 28 through the hollow piston 27 to the sump 44. Simultaneously, also, the back up solenoid 62 is energized allowing oil pressure from the pump 45 to return the back to normal (raised) position.

The thermal relay 136 maintains a closed circuit of its contacts until warping of the bimetallic strip 136a opens its contacts. All relays now return to normal position, with the chair in the normal position shown in FIG. 1.

In the foregoing description certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, the operation, and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby; the new and useful construction, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the disclosure.

We claim:

1. Control means for a dental chair having a hydraulic cylinder operated jack, a chair seat pivotally connected to the jack, a seat back pivotally connected to the chair seat, hydraulic cylinder means for tilting the chair seat, and hydraulic cylinder means for raising and lowering the seat back, said control means including a motor-driven pump, a fluid circuit including an oil sump to which the motor-driven pumps is connected and to which oil from the cylinders is returned, solenoid valves in said fluid circuit, an electric circuit in which the motor and solenoids are located, and electrical switch means in the electric circuit inluding separate eletrical switches for independently selectively energizing the proper solenoids for independently controlling the jack cylinder, the chair seat cylinder and the seat back cylinder, and a single electrical switch for energizing the proper combination of solenoids for simultaneously operating all of the cylinders for returning the pack, the chair seat and the seat back to normal positions, said electrical switch means simultaneously operating the pump motor, a motor relay and a solenoid relay located in said electric circuit, and a thermal relay in the electric circuit controlling said other two relays.

2. Control means for a dental chair having a hydraulic cylinder operated jack, a chair seat pivotally connected to the jack, a seat back pivotally connected to the chair seat, hydraulic cylinder means for tilting the chair seat,

and hydraulic cylinder means for raising and lowering the seat back, said control means including a motordriven pump, a fluid circuit including an oil sump to which the motor-driven pump is connected and to which oil from the cylinders is returned, solenoid valves in said fiuicl circuit, an electric circuit in which the motor and solenoids are located, and electrical switch means in the electric circuit including separate electrical switches for independently selectively energizing the proper solenoids for independently controlling the jack cylinder, the chair seat cylinder and the seat back cylinder, and a single electrical switch for energizing the proper combination of solenoids for simultaneously operating all of the cylinders for returning the jack, the chair seat and the seat back to normal positions, said electrical switch means simultaneously operating the pump motor, solenoid valves in the fluid circuit between the motor-driven pump and each of the cylinders, solenoid valves in the fluid circuit between each of the cylinders and the oil sump, a motor relay in the electric circuit which controls operation of the motor-driven pump, a solenoid relay in the electric circuit which controls operation of the solenoid valves, and a thermal relay in the electric circuit which controls said other two relays.

3. Control means for a dental chair as defined in claim 1 in which the jack cylinder and the seat back cylinder are single acting cylinders and the seat tilting cylinder is a double acting cylinder.

4. Control means for a dental chair as defined in claim 1 in which solenoid valves are located in the fluid circuit between the motor and each of the cylinders, and solenoid valves are located in the fluid circuit between each of the cylinders and the oil sump.

5. Control means for a dental chair as defined in claim 3 in which a solenoid valve is located in the fluid circuit between the pump and each of the single acting cylinders, a solenoid valve is located in the fluid circuit between the pump and each end of the double acting cylinders, a solenoid valve is located in the fluid circuit between each single acting cylinder and the oil sump, and a solenoid valve is located in the fluid circuit between each end of the double acting cylinder and the oil sump.

6. Control means for a dental chair as defined in claim 3 in which a jack up solenoid valve is located in the fluid circuit between the motor driven pump and the jack cylinder, a jack down solenoid valve is located in the fluid circuit between the jack cylinder and the oil sump, a back up solenoid valve is located in the fluid circuit between the pump and the back cylinder, a back down solenoid is located between the back cylinder and the oil sump, a seat up solenoid valve is located between the pump and one end of the seat tilting cylinder, a seat down exhaust solenoid valve is located between said one end of the seat tilting cylinder and the oil sump, a seat down solenoid valve is located between the pump and the other end of the seat tilting cylinder, and a seat up exhaust solenoid valve is located between said other end of the seat tilting cylinder and the oil sump.

7. Control means for a dental chair as defined in claim 6 in which a back up and back down electrical switch in the electric circuit alternately closes the electric circuit simultaneously to the back up solenoid valve and the pump motor and to the back down solenoid valve, a seat up and seat down electrical switch in the electric circuit alternately closes the circuit simultaneously to the pump motor, the seat up solenoid valve and the seat up exhaust solenoid valve, or simultaneously to the pump motor, the seat down solenoid valve and the seat down exhaust solenoid valve, a jack up and jack down electrical switch alternately closes the circuit simultaneously to the pump motor and the jack up solenoid valve or to the jack down solenoid valve, and a return electrical switch in the electric circuit simultaneously closes the circuit to the pump motor, the back up solenoid valve, the seat down solenoid valve, the seat down ex- 1 1 haust solenoid valve and the jack down solenoid valve. 8. Control means for a dental chair as defined in claim 6 in which a cushion valve is located in the fluid circuit between the jack down solenoid valve and the oil sump. 9. Control means for a dental chair as defined in claim 6 in which the seat up solenoid valve, seat down solenoid valve and back up solenoid valve are connected to an inlet manifold communicating with the motor driven pump, and the seat down exhaust solenoid valve, seat up exhaust solenoid valve and back down solenoid valve are connected to an exhaust manifold communicating with the oil sump.

References Cited UNITED STATES PATENTS JAMES T. MCCALL, Primary Examiner U.S. Cl. X.R.

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