Field of the invention

The present invention relates to an adjustable headrest mech anism of a treatment chair, which allows adjustments relative to the back section of the chair. Often in medical and dental treatment situations, treatment chairs are provided with an adjustable headrest. The headrest is often connected to the back section in the treatment chair with an adjustable head rest member. Focus has been to produce easily adjustable headrests but nowadays the problem is to produce a durable and strong adjustable headrest for today's patients. Obesity and weight of the patients have increased among the popula tions worldwide. Adjustable headrests have a weak point in their mechanical adjusting construction and design since in creasing number of heavier people easily exceed the weight limits of the headrest adjusting mechanisms. This results malfunctional, deformed, worn and broken headrest position adjusting mechanisms at dentist receptions and also else where. The strength and quality of the position adjustment mechanism of the treatment chair is essential for durability in daily use.

The headrest is connected to the upper section of the treat ment chair's back section with the help of a position adjust ment member and is adjusted with it relative to the chair back section to fit for every patient's physical body shape. One problem is that the adjusting mechanism and its locking systems are heavily overloaded when today's heavier patients are treated during operation. Background of the invention

The present invention relates to a problem of insufficient rigidity and durability of adjustable headrest mechanisms un der use with heavy patients. The present invention relates to rigidness, strength and durability of the adjusting mechanism connected to the headrest and the back section of the treat ment chair. Preferably the rigidness and robust construction are achieved by using square-shaped pawl elements with flat counter surface to resist heavy loads.

Object of the invention

The object of the present invention is to achieve a quickly adjustable and easily usable adjusting mechanism for head rests in treatment chairs with small adjusting steps, which mechanism is user-friendly and also hygienic, silent and du rable with high resistance to heavy loads.

The adjusting mechanism according to the invention is charac terized by what is disclosed in the characterization part of claim 1. Other embodiments of the invention are characterized by what is disclosed in the other claims.

Brief Description of the Invention

The present invention provides an adjusting mechanism having at least one cylindrical ratchet element comprising several parallel rows of recesses, several pawls and a release mecha nism to withdraw the pawl heads from the recesses. The pawl heads and the recesses on the cylindrical ratchet element are formed to correspond each other. In each row, the recesses are arranged one after the other on the periphery of the ratchet element at an angular distance from each other and all the recesses in the same row are on the same plane of ro tation. The rotational motion of each recess is only a part of the whole circle. Preferably, the plane of rotation of each row of recesses is centered with the vertical plane go ing through the longitudinal center line of the pawl with which each row of recesses is in contact.

The parallel rows of recesses are arranged so that only one pawl at a time may enter in a recess. That is achieved by ar ranging the position of each row of recesses by a required angle. The recesses are arranged e.g. according to the Verni er principle. With a set of several parallel pawls the inven tion provides an adjustment mechanism with sufficiently small adjustment steps and high weight resistance. A spring at the second end of each pawl is arranged to press the pawl's head to the nearest recess on the cylindrical ratchet element. The release mechanism is arranged to move all the pawls when ac tuating the release handle but only one pawl head at a time is withdrawn and released from the recess of the cylindrical ratchet element while other pawls are following the outer surface of the cylindrical ratchet element.

The adjusting mechanism comprise a rigid frame and a rigid lid, which compensate the unsymmetrical stress, which can oc cur when a pawl not in middle is accommodated inside a recess and taking up the load. The adjustment mechanism according to the invention comprises several parallel pawls where the pawl heads are shaped to fit into the recesses on the cylindrical ratchet element. The recesses are organized so that only one pawl head at a time can be in a locking position inside a re cess.

Advantages of the Invention

The materials of the new mechanism can withstand heavy loads and the mechanism can be safely adjusted as needed. Safety is also enhanced by the fact that, if one of the load-bearing pawls is damaged or even broken, the next pawl will take over the load after 5-10° degrees rotation. Such a small movement will minimize the chance of an injury.

In some known solutions, when adjusting the headrest accord ing to the patient's position, the adjustment requires both hands to be used by the operator of the chair. One hand re duces the pressure on the headrest mechanism and the other hand simultaneously presses the release lever located on the side of the mechanism. The lever must be pressed regardless of whether the joints of the mechanics are adjusted up or down. Since the treatment work is mainly done with sterile gloves in the hands, the headrest must be carefully cleaned when changing patients, which creates requirements for the cleaning of the surfaces.

The new arrangement facilitates the treatment work of the treatment staff. Both joints of the headrest construction can turn up without pressing the release lever. The pawls are ar ranged so that they can withdraw from the recesses along the sloping surface of the recesses allowing the cylindrical ratchet element to rotate relatively to the pawls. The spring at the second end of each pawl tends to press the pawl's head into the nearest recess, to which it locks when lifting of the headrest is stopped. Both joints are arranged to lock in the position where the lifting is stopped. The release lever does not need to be pressed and the headrest can be adjusted upwards with one hand, either both joints simultaneously or only one joint alone. The adjustment can also be done without touching the palm of the hand, for example lifting with the wrist or even with the knee. This greatly speeds up the ad justment and at least one hand remains sterile. The downward adjustment is made for safety reasons so that the other hand will lighten the headrest and the patient's head and the oth er hand will release the locked joints from the release lev er. At the end of the adjustment the release lever is freed and the both headrest joints lock into the next recesses. The shape of both the pawl heads is shaped so that the load does not cause the pawl heads to break out of the recess but in stead tends to lock into the recess to ensure a reliable locking.

One advantage of the solution according to the invention is that the structure is adjustable in extremely small steps, and it is rigid, strong, durable, quickly adjustable, easy to use and also hygienic. Rigidness and strength are achieved by maximizing the pawl head's contact area on the load bearing surfaces of the recesses. Preferably, the counter surface ar ea is maximized, for instance, by using pawls with square cross-section instead of round pawls.

The small or dense gradation in adjusting the headrest is achieved by increasing the number of the pawls and rows of recesses on the cylindrical ratchet element. For every pawl head the cylindrical ratchet element has a row of recesses to be fitted in, and every row of recesses is arranged to a cer tain angle relative to the other rows of recesses. This ena bles a dense locking positioning when locking the headrest. Implementing the Vernier principle with placing the pawls on the cylindrical ratchet element ensures that one pawl head at a time is inserted inside one recess.

The recesses are formed corresponding to the pawl heads, in the way that their relative movement is possible only in one direction. That makes the headrest position adjustment member to operate like a ratchet, free movement to one direction and locked to the other direction. The attached pawl release mechanism unlocks the pawls and allows the movement to both directions to adjust the headrest to a desired position when all pawl heads are withdrawn from the recesses.

List of figures

In the following, the invention will be described in detail by the aid of example embodiments by referring to the at tached simplified and diagrammatic drawings, wherein

FIG. 1 presents in a side view a treatment chair compris ing a headrest and its position adjustment member according to the invention,

FIG. 2 presents in a side view a headrest with its posi tion adjustment member according to the invention, FIG. 3 presents in a side view a headrest with its posi tion adjustment member according to the invention, the adjustment member cross-sectioned,

FIG. 4 presents in a side view and cross-sectioned a posi- tion adjustment member according to the invention,

FIG. 5 presents in a side view an enlarged cross-section of a ratchet mechanism of a position adjustment member according to the invention,

FIG. 6 presents in a side view a headrest according to the invention without its position adjustment member so that its fastening lugs of one side are visible,

FIG. 7 presents in a side view a cross-section of a posi tion adjustment member according to the invention without the ratchet mechanisms, FIG. 8 presents in an oblique view the inner parts of a position adjustment member according to the inven tion,

FIG. 9 presents in a top view an enlarged corner of the inside of a position adjustment member according to the invention,

FIG. 10 presents in an oblique view a pawl or pawl element of a position adjustment member according to the invention, and FIG. 11 presents in an oblique view a cylindrical ratchet element of a position adjustment member according to the invention.

Detailed description of the invention

In order to achieve the objects mentioned above, the present invention provides a strong and robust position adjustment member connected between the headrest arm and the headrest of a treatment chair. The structure of the headrest and its com ponents are presented in the figures in a schematic and sim plified way. In that case all the components and forms of the structures are not necessarily presented.

Fig. 1 presents in a side view a treatment chair 1 comprising a headrest 2, a position adjustment member 3 according to the invention, a headrest arm 4, a back section la, a seat sec tion lb and a leg section lc. The position adjustment member 3 comprises a lockable joint 3a at both of ends of its frame 3b, which joints 3a allow the headrest 2 to be positioned and adjusted in relation to the back section la.

Fig. 2 presents in a side view an advantageous embodiment of the invention. The headrest 2 has two parallel fastening lugs 2a with which the headrest 2 is articulated to the first joint 3a of the position adjustment member 3. Corresponding ly, the second end of the position adjustment member 3 is ar ticulated with the second joint 3a to the two parallel fas tening lugs 4a of the headrest arm 4. Thus, the headrest 2 can be turned around the first joint 3a in relation to the position adjustment member 3 and the position adjustment mem- ber 3 can be turned around the second joint 3a in relation to the headrest arm 4 that is inserted into the back section la of the treatment chair 1.

In addition, the position adjustment member 3 comprises a re lease member 13 for unlocking the joints 3a to adjust the headrest 2 into another desired position.

Figs. 3-5 present in a side view different cross-sections of the position adjustment member 3 of the invention. In Fig. 3 the first part of the components of the position adjustment member 3 is visible and in Fig. 4 the second part of the com ponents of the position adjustment member 3 is visible. Fig 5. presents an enlarged cross-section of a ratchet mechanism 5 of the position adjustment member 3 according to the inven tion.

As mentioned above, the position adjustment member 3 compris es the frame 3b and the joint 3a at each end of the frame 3b. For each joint 3a the frame 3b comprises a round fulcrum hole 3c at each of its end and the ratchet mechanism 5 inside the frame 3b. The ratchet mechanism 5 comprises a cylindrical ratchet element 6 that acts also as a fulcrum pin and is placed inside the fulcrum hole 3c at each end of the frame 3b. The cylindrical ratchet element 6 comprises a group of parallel rows of recesses 6a on its cylindrical surface.

The ratchet mechanism 5 further comprises a group of parallel pawls 7 and springs 8, and a counter element 3d that is fix edly fastened to the frame 3b. The springs 8 are arranged to press the pawls 7 towards the cylindrical ratchet element 6 in order to bring the head of the pawl 7 in contact with the row of the recesses 6a. The pawl 7 is arranged to prevent the rotation of the cylindrical ratchet element 6 in one direc tion when the pawl 7 is entered into a recess 6a. A rotation to the other direction is not prevented.

The position adjustment member 3 also comprises a release mechanism 10 with its guide element 9, which release mecha nism 10 is arranged to allow the rotation of the cylindrical ratchet element 6 in both directions by pulling the pawl 7 out from the recess 6a when the release member 13 is pressed. For that purpose, the pawl 7 has a release pin 7a.

In addition, the position adjustment member 3 comprises a bottom element 11 inside the frame 3b. The bottom element 11 is arranged to support the pawls 7 which prevent the cylin drical ratchet element 6 from rotating in the fulcrum hole 3c at the first end of the frame 3b. The corresponding support arrangement is at the second end of the frame 3b.

Fig. 5 presents in a side view an enlarged cross-section of an advantageous ratchet mechanism 5 of a position adjustment member 3 according to the invention. The recesses 6a of the cylindrical ratchet element 6 have a counter surface 6b and a support surface 6c. When a recess 6 turns into the same line with a pawl 7 the pawl 7 is pushed into the recess 6a by the spring 8 associated with the pawl 7 and placed between the pawl 7 and the counter element 3d. The linear motion of the pawl 7 is stopped by the counter surface 6b and the support surface 6c is pressed against the pawl 7 by the pressure caused by the headrest 2. Fig. 6 presents in a side view a headrest 2 and the first end of the headrest arm 4 according to the invention without the position adjustment member 3 so that their fastening lugs 2a and 4a of one side are visible. The fastening lugs 2a of the headrest 2 comprise square coupling elements 2b and the fas tening lugs 4a of the headrest arm 4 comprise square coupling elements 4b. The coupling elements 2b, 4b are arranged to connect the cylindrical ratchet element 6 immovably to the fastening lugs 2a, 4a. This means that the first cylindrical ratchet element 6 placed into the coupling elements 2b does not move or rotate in relation to the headrest 2 and the sec ond cylindrical ratchet element 6 placed into the coupling elements 4b does not move or rotate in relation to the head rest arm 4.

Fig. 7 presents in a side view a cross-section of a position adjustment member 3 according to the invention without the ratchet mechanisms 6. The fulcrum holes 3c that act as rota tion chambers of the cylindrical ratchet elements 6 are empty and two of the guide rails 12 for the pawls 7 above the bot tom 11 are visible.

Figs. 8 and 9 present an advantageous headrest position ad justment member 3 according to the invention without its cov er. Fig. 8 presents the headrest position adjustment member 3 in an oblique top view. The mechanical construction of the headrest position adjustment member 3 comprises at least one cylindrical ratchet element 6 with several rows of recesses 6a. For each row of recesses 6a the adjustment mechanism com prises a corresponding pawl 7. The pawls 7 and recesses 6a are arranged to locate relatively so that only one pawl's head 7c at a time can be accommodated inside a recess 6a.

In the situation of Figs. 8 and 9 the head 7c of the upper most pawl 7 is accommodated inside a recess 6a and is there fore responsible for locking the first direction of rotation of the cylindrical ratchet element 6 of the joint 3a between the headrest arm 4 and the position adjustable member 3.

The release mechanism 10 is arranged to withdraw the pawl head 7c from the recess 6a by actuating the release pin 7a. The release mechanism 10 comprises a set of release members 10a, which are in this embodiment diagonal edges in a frame plate of the release mechanism 10. The diagonal edges are in contact with release pins 7a so that when the release member 13 is pressed the diagonal edges in the frame plate draw all the pawls 7 outwards from the ratchet element 6.

Withdrawing the pawl heads 7c from the recess 6a by operating the release member 13 disables the ratchet function and re leases the joints 3a at the ends of the position adjustment member 3 so that the position adjustment member 3 and the headrest 2 can be turned to both directions.

Fig. 9 presents in a top view a part of the position adjust ing member 3 without its cover. For the sake of clarity, the second uppermost pawl 7 in the figure has been cut so that the end of the guide rails 12 between the parallel pawls 7 are better noticeable. Also, in this situation the head 7c of the uppermost pawl 7 is accommodated inside a recess 6a. Fig. 10 presents in an oblique top view a pawl or pawl ele ment 7 according to the invention. In addition to the frame part with a square cross section the pawl 7 comprises a head part 7c, a release pin 7a, a spring guide 7b, a damper 7d and a slant recess 7e at the head of the pawl 7. The head part 7c is fitted to match with the form of the recess 6a of the ratchet element 6. The damper 7d can be e.g. a rubber pad in the head part 7c of the pawl 7. The slant recess 7e forms a contact surface with the support surfaces 6c of the recesses 6a of the ratchet element 6 on that side of the pawl 7 which is in contact with the support surfaces 6c. Preferably, the slant recess 7e becomes deeper from the first end of the pawl 7, where the head part 7c is, towards the second end of the pawl 7. The slanting contact surface of the slant recess 7e prevents the head of the pawl 7 from accidentally disengaging from inside the recess 6a when the position of the headrest 2 is adjusted. This improves safety.

Fig. 11 presents in an oblique top view a cylindrical ratchet element 6 according to the invention. The surface of the cy lindrical ratchet element 6 comprises several parallel rows of recesses 6a. Preferably, each row cover only a part of the whole periphery of the ratchet element 6. For instance, one row may have five recesses 6a which are placed at intervals of 40 degrees. With five parallel similar rows where each row is shifted 8 degrees from its adjacent row 25 different lock ing places are achieved at 8 degrees intervals.

As mentioned in the description above, the recesses 6a com prise two surfaces, a curvilinear counter surface 6b and a flat support surface 6c. Preferably, the angle between the counter surface 6b and the support surface 6c is 90 degrees, but it may also be another angle depending on the shape of the head part 7c of the pawl 7.

The rows of recesses 6a are arranged to a certain angle rela tive to the other rows of recesses 6a. With a set of parallel pawls 7, this allows a dense adjustment, locking and posi tioning of the headrest 2 despite a robust and strong con struction. The cylindrical ratchet element 6 comprise square fastening ends 6d to be installed into the fastening lugs 2a and 4a to prevent the first ratchet element 6 from rotating in relation to the headrest 2 and the second ratchet element 6 from rotating in relation to the headrest arm 4. Thus, the first ratchet mechanism 5 is non-rotatably connected with the headrest 2 and the second ratchet mechanism 5 is non- rotatably connected with the headrest arm 4.

As described above, moving the headrest 2 and/or the position adjustment member 3 will cause the cylindrical ratchet ele ment 6 to move relatively to the pawls 7. And because the rows of recesses 6a are arranged to a certain angle relative to each other each of the pawl heads 7c are pushed one at a time into a recess 6a corresponding in their row of recesses 6a when a certain rotation angle is achieved.

It is obvious to the person skilled in the art that the in vention is not restricted to the examples described above but that it may be varied within the scope of the claims present ed below. Thus, for instance the design of the pawl heads can vary and therefore the inner surfaces and of the recesses can vary correspondingly. It is also obvious to the person skilled in the art that the cross-section of the pawls need not necessarily be square. It can be, for instance, rectangular or any suitable shape that makes it possible to construct a reliable, strong and robust device structure.