U.S. patent number 3,874,728 [Application Number 05/407,179] was granted by the patent office on 1975-04-01 for dental patients chair with a parallelogram supporting arm.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Rolf-Jurgen Weiland.
United States Patent |
3,874,728 |
Weiland |
April 1, 1975 |
DENTAL PATIENTS CHAIR WITH A PARALLELOGRAM SUPPORTING ARM
Abstract
A dental patient's chair with a parallelogram supporting arm
having one end linked to a base and another end carrying the seat
of the chair and with an adjusting device for the height shifting
of the chair. The invention is particularly characterized in that
the adjusting device is a spindle drive actuated by electromotor
and engaging the supporting arm preferably between two diagonally
opposed link axes of the arm ends.
Inventors: |
Weiland; Rolf-Jurgen
(Lortzenbach, Furth, DT) |
Assignee: |
Siemens Aktiengesellschaft
(Erlangen, DT)
|
Family
ID: |
5859751 |
Appl.
No.: |
05/407,179 |
Filed: |
October 17, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Oct 21, 1972 [DT] |
|
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2251808 |
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Current U.S.
Class: |
297/330;
248/421 |
Current CPC
Class: |
A61G
15/02 (20130101) |
Current International
Class: |
A61G
15/00 (20060101); A61G 15/02 (20060101); A47c
001/02 (); A47c 001/06 () |
Field of
Search: |
;297/330,345-347
;108/147 ;248/419-422 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nunberg; Casmir A.
Attorney, Agent or Firm: Richards & Geier
Claims
I claim:
1. A dental patients' chair, comprising a base, a seat, a
parallelogram carrying arm having one end connected with said base
and the other end carrying said seat, the ends of said arm having
diagonally opposed axles, and a device for height shifting of the
seat, said device comprising an electrically driven spindle drive
engaging said arm between said axles, said spindle drive comprising
a motor, a rotary spindle driven by said motor, a bearing for the
spindle connected with one of said axles and a screw nut engaging
said spindle and connected with that end of the arm having the
other one of said axles.
2. A chair according to claim 1, wherein said bearing for the
spindle is connected with the one axle which is connected with said
base and wherein said driving motor for the spindle is located
outside of said arm on said base.
3. A chair according to claim 2, having an intermidiate shaft
connected with said motor and transmitting the drive of said motor
to said spindle.
4. A chair according to claim 3, having an axle supporting said
intermidiate shaft, the last-mentioned axle being in alignment with
said one axle.
5. A chair according to claim 4, wherein the last-mentioned axle
and said one axle form a continuous axle bearing.
6. A chair according to claim 4, wherein said intermediate shaft is
removable from said one axle.
7. A chair according to claim 6, comprising a plug axle and two
opposed bearings for said one axle and supporting said plug axle,
said intermediate shaft being rotatably mounted upon said plug
axle.
8. A chair according to claim 7, wherein said opposed bearings are
axially movable and wherein said plug axle is a clamping screw for
connecting the bearings of said one axle with the bearings of said
intermediate shaft.
9. A chair according to claim 8, wherein said spindle drive
comprises a safety switch operable when subjected to tension for
interrupting the circuit of said driving motor.
10. A chair according to claim 9, wherein said spindle has
transversely separated non-rotary portions, means interconnecting
said portions when subjected to rotary moment and separating said
portions when subjected to pull, said safety switch being located
between said portions.
Description
This invention relates to a dental patients' chair with a
parallelogram supporting arm having one end linked to a base and
another end carrying the seat of the chair and with an adjusting
device for the height shifting of the chair.
Various treating methods and different sizes of patients make it
necessary to be able to change the seat carrying upper part of a
dental treating chair in relation to its height within wide limits.
Particularly when the patients are of large size and the treating
person is sitting, it is necessary to be able to bring the chair
into a particularly deep position. Carrying arms having the shape
of parallelograms were found particularly suitable for this purpose
since they can bring a chair into a deep position which is actually
limited only by the height of the parallelogram arm which is quite
small as compared to other height adjusting devices suitable for
these purposes. Another advantage of the parallelogram carrying arm
is that its linking to the base requires little space, so that
there is sufficient freedom for the feet of the treating person.
Hydraulic lifting devices (piston-cylinder arrangements) have been
used for the height adjustment of the parallelogram arm of such
patients' chairs, since they can raise the weight of the heavy
upper chair part along with the patient at most inconvenient lever
arrangements in the deepest end position (pressure forces in the
size of more than one thousand kilopond). Furthermore, they are so
small that it is possible to provide them in a sufficiently narrow
parallelogram carrier. (A widening of parallelogram arms would make
difficult an easy movement of the doctor to the chair or the
patient and would affect his work). However, it is necessary to
accept the drawback of these hydraulic devices consisting in that
devices cannot be obtained which are sufficiently oil tight. It was
found that in the course of years these leakage losses dirty the
lower chair portions and the floor of the treating room. Chair
parts dirtied by oil can be cleaned only with considerable expense
and loss of time which cannot be compensated.
An object of the present invention is to provide a dental patients'
chair of the described type which can produce the high pressure
forces required for adjusting the chair without it being necessary
to substantially increase the size of the parallelogram arm, which
can be operated more simply and which cannot produce dirt by oil
through oil leakage. Another object is the diminution of costs of
making the chair.
Other objects of the present invention will become apparent in the
course of the following specification.
In the accomplishment of the objectives of the present invention it
was found desirable to provide as the adjusting device a spindle
drive actuated by electromotor and engaging the parallelogram
supporting arm preferably between two diagonally opposed link axes
of the arm ends.
The use of the spindle drive not only eliminates the
above-mentioned drawbacks of known devices but also has the
advantage that substantially fewer structural parts are necessary.
Furthermore, the transporting and the mounting are simplified since
there are no more dependent drives for shifting the back and
adjusting the seat by means of the parallelogram arm, as is the
case in known chairs. There it was necessary to apply pressure upon
oil transmitted by an oil pump located in the base in addition to
the hydraulic circuit for the carrying arm, also in the hydraulic
circuit of the raising device for moving the back, which is located
in the upper part of the chair.
In accordance with an advantageous embodiment of the present
invention it is suggested that the spindle drive should be a roller
screw drive, preferably a ball spindle drive. It is advantageous to
switch a self-locking drive in front of the roller screw drive
since this eliminates the use of more expensive means for locking
the driving motor when standing still. The driving motor can be
arranged in or outside of the parallelogram carrying arm. Since the
parallelogram carrying arm due to its box-like structure
constitutes a hollow body with good resonance properties which
could strengthen the noises of the motor, it is advantageous to
arrange the motor outside of the parallelogram carrying arm. This
also eliminates sound absorbing provisions which are difficult to
attain. The advantageous arrangement of the driving motor arranged
outside the supporting arm has the further advantage that the motor
is easier to reach (for exchange of brushes, belts etc.).
The connection of the spindle or spindle nut to the diagonally
extending link axes of the supporting arm is not absolutely
necessary but is advantageous since it avoid undesirable bending
forces which could affect parallelogram rods.
Within the scope of the present invention it is possible to select
the location of the spindle and spindle nut upon the upper or the
lower link axis. However, it is advantageous to connect the drive
to the link axis located at the side of the base, since this
provides a comparatively short distance for transmitting the rotary
movement of the motor to the spindle.
The invention will appear more clearly from the following detailed
description when taken in connection with the accompanying drawings
showing by way of example only, preferred embodiments of the
inventive idea.
In the drawings:
FIG. 1 is a perspective view of a dental chair.
FIG. 2 is a perspective view of the base of the chair.
FIG. 3 is a partial perspective view of a different chair base.
FIG. 4 is a partial perspective view showing the parallelogram
carrying arm of FIG. 1 in its lowermost position.
FIG. 5 is a partial top view of the same carrying arm.
FIG. 6 is a partial sectional view showing the axial bearing of the
arm.
FIG. 7 is a partial sectional view showing the spindle drive of the
arm.
FIG. 1 shows a dental patients' chair having a base 1 to which the
parallelogram carrying arm 2 is connected. A support 3 is arranged
at the free end of the arm and carries the chair upper part
consisting substantially of the back 4 and the seat 5. The back 4
can be inclined about the axis 6 relatively to the seat 5 and the
seat 5 can be tipped relatively to the carrier 3 about an axis also
extending transversely to the longitudinal axis of the chair which
is not shown in the drawing. The three adjusting movements, namely,
the inclination of the back, the tipping of the seat and the height
adjustment of the upper part of the chair are actuated by means of
the parallelogram carrying arm by actuating members 7 to 9 provided
upon the back 4. The actuating members 7 to 9 are located upon the
upper part of the back 4 and are so arranged that they can be
operated from the back surface of the back as well as from its
upper side. The back is made very thin so as to provide a
sufficient freedom of foot movement for the seated person in the
lower chair position when the back is substantially vertical. In
order to avoid extending parts the actuating members 7 to 9 are
embedded in the chair back.
The base 1 consists substantially of a bottom part 11 upon the
front portion of which on opposite sides are provided two vertical
side pieces 12, 13 in which the parallelogram arm 2 is swingably
mounted. The side pieces 12, 13 are covered by removable covering
sheets 17, 18. The parallelogram 2 can be moved from the
illustrated position into a deep position in which the arm extends
substantially horizontally (FIG. 4). In the back part of the bottom
11 there is a stepping plate 14 which is swingably mounted and
which cooperates with switching members in the base 11 in such
manner that when the plate 14 is stepped on the drive for moving
the parallelogram 2 is switched off. This arrangement serves for
the safety of the operator if by mistake an object (foot of the
operator or chair) reaches into the moving range of the carrier 3
or the parallelogram carrier 2 during the downward movement of the
chair.
The base 1 consists of a welded structure formed by a plate 15
which can be fixed to the floor, a box-shaped cover 16 and side
pieces 12, 13 welded on both sides of the part 16 to the plate 15.
Each of the side pieces 12, 13 consists of two half shells 19, 20
welded to each other and held by space supports 21. The half shells
are made of sheet metal (drawn or pressed part). Bushings
supporting the bearing axles 22 and 24 of the parallelogram arm are
welded in the half shells 19, 20. The cover 16 is made of a sheet
plate by suitable cutting and edge forming. Within the box which is
thus formed there are provided sheet profiles 26 which are welded
both to the cover 16 and to the plate 15 and extend parallel to the
longitudinal sides of the base plate. The sheet profiles are also
produced in a bending process. At its rear end the cover 16 has a
recess which forms with the base plate 16 an open box 27 containing
two switches 28 as well as different electrical connecting parts
29. The switches 28 are actuated by the stepping plate 14 shown in
FIG. 1.
FIG. 3 shows a different construction of a welded base for
supporting the parallelogram carrying arm 2. Here the basic part is
constituted by a base plate 30 and welded four edged hollow profile
rods 31, 32. The hollow profile rods 31, 32 provide a safe frame
free from windings. Upon the frame is provided a sheet covering 33.
The side pieces for supporting the parallelogram carrying arm
consist of struts 34 to 37 which are welded together also from
hollow profile rods.
The two welded constructions are technically very easy to
manufacture, they have a low transportation weight and are very
suitable for receiving side loads. The last-described construction
is particularly easy to produce without a great use of special
tools.
FIG. 4 shows the parallelogram carrying arm 2 swingably connected
to the base 1 in its lowermost position. The drawing shows the
parallelogram carrying arm partly in section for better
illustration of its adjusting means. The parallelogram arm 2
consists substantially of two halves 40 and 41, whereby the upper
half 40 is swingably connected on the one hand by an axle 22 to the
side pieces 12, 13 and on the other hand is connected by an axle 23
to the carrier 3. The lower carrying arm half 41 is also connected
to the side pieces 12, 13 by an axle 24 and is mounted in the
carrier 3 by an axle 25. The movement of the parallelogram arm 2
and thus of the carrier 3 for the upper part 4, 5 of the chair,
takes place by an electromechanical drive consisting of an
electromotor 39, a drive 46 and a ball revolving spindle 47. The
motor 39 is mounted upon the base plate 15 outside of the
box-shaped parallelogram carrying arm 2. The power transmission
from the motor takes place by a V-belt 48 and a roller 49 and from
there through a further V-belt 50 to the driving shaft 51 of a worm
gear to which the rotary spindle 58 of the spindle drive 47 is
connected on the side away from the drive. The motor is fixed to a
holding device 52 adjustably connected to the base plate 15 for
tensioning the V-belt 48. The V-belt 48 can receive the necessary
belt tension by a tensioning screw 53.
The drive 46 is connected by a pin 45 flanged thereto to the axle
24. The spindle nut 54 is connected to the axle 23, so that the
spindle drive engages between the diagonal axles 23, 24 of the
parallelogram rectangle 22 to 25. For easier accessibility the
motor 39 is covered by a removable cover 57.
FIG. 5 shows the parallelogram carrying arm in top view, some parts
of the arm and coverings being also sectioned. The roller 49 is a
part of an intermediate shaft 60 which can be easily removed from
the axle bearing 24 for the replacement of the V-belts 48 and 50.
Details of the axle bearing 24 are shown in FIG. 6.
The lower half 41 of the parallelogram carrying arm 2 is supported
on the one hand by a bolt 62 and a sliding bearing 63 in the side
piece 13 and on the other hand by a further bolt 64 and a further
sliding bearing 65 in the side piece 12. The intermediate shaft 60
is rotatably mounted by two ball bearings 66, 67 upon a plug axle
68 serving as a bearing axle. An inner six edge screw is used as
the plug axle, which engages on the one hand with its head a joint
of the bearing part 62 and on the other hand is screwed into the
bearing bolt 64. The two bearing bolts 62, 64 are protected against
rotation by radially directed screws 69, 70. When the plug axles 68
are screwed into the bearing bolt 64, the inner rings of the ball
bearings 66, 67 are pressed against the front surfaces of the
bearing bolts 62 and 64, so that the bearings of the intermediate
shaft are tensioned.
The removal of the intermediate shaft 60 for exchanging a V-belt
takes place by unscrewing the plug axle 68 by a few turnings out of
the bolt 64. Then the fixing screw 70 is released and the bearing
bolt 64 is easily pressed outwardly by a light hitting upon the
head of the axle 68. The outer movement of the bearing 64
relatively to the bolt 62 releases the bearing tension. After the
axle 68 has been completely screwed out, the intermediate roller 60
can be removed.
FIG. 7 shows partly in longitudinal section the spindle drive 47
engaging on the one hand the axle bearing 24 (at the bearing bolt
64) and on the other hand the spindle drive 47 engaging the axle
bearing 23. The drive 46 which is in general use, is screwed to a
flange of the bolt 45. The sectional view of FIG. 7 shows the inner
structure of the spindle nut 54. The spindle nut 54 is transversely
separated at the location 71 into a part 72 containing the rotary
ball part and a part 74 receiving a switch 73 and connected with
the axle bearing 23. Both parts 72 and 74 are screwed together by
three circumferentially located screws 75 while leaving a small
axial play 76. Since in normal conditions the entire spindle drive
is loaded solely by pressure, the three screws 75 serve only to
transmit the action transmitted from the driving spindle 58 to the
spindle nuts 72, 74. If, however, the driving spindle is subjected
to pull, then the two parts 72 and 74 are raised from each other.
When the two parts are separated, the switch 73 fixed to the part
74 is switched on, since the actuating pin 76 is raised from its
support 77 (part of 72). The switch 73 is included in the circuit
of the driving motor 39, so that when the switch is actuated the
motor stops immediately.
The spindle 58 has a rise of about 12 mm. In its screw threads
within the range of the part 72 are located balls 78 which are
placed next to each other as an endless chain. When the spindle is
rotated the balls move in the screw thread passages. During one
direction of rotation of the spindle the balls leave the screw
thread passages at the location 79 and run into a channel 80 of the
part 72, where they move out of the opening 81 and move back into
the screw thread passages of the spindle. The movement of the balls
is reversed in the opposite direction of rotation.
* * * * *