A device for fixing the hub of an arm of a wind-screen wiper (2) on a pivoting axis (1) with locking elements (6, 7) for the arm on the pivoting axis (1), a cavity (32) which is created in the hub (2) and is provided with adjusting and angular positioning elements for the arm in relation to the axis (1), whereby the hub (2) rests on the base of a stop (3) which nestles on a radius of operation (4) of the said axis (1); the locking elements (6, 7) are adapted in such a way that they can be engaged in a locking or unlocking position, the adjusting elements includes a connecting ring (10) which is rotationally fixed to the axis (1) and accommodated in the cavity (32) of the hub (2) with a certain amount of play allowing for limited relative angular displacement between the connecting ring (10) and the hub (2) when the locking elements (6, 7) are in an unlocked position, whereby all relative displacement is prohibited between the connecting ring (10) and the hub (2) when the locking elements (6, 7) are in a locked position.

The present invention relates to a windshield wiper arm fixing device, in particular for windshields of automotive vehicles.
The importance of reliable and correct fixing of such equipment to the performance of the windshield wipers and therefore to safe driving of the vehicle in rainy or snowy weather is well known. In the devices most widely used at present, the ends of the oscillating spindles to which the windshield wiper arms are fixed have a screwthreaded part onto which is screwed a nut for locking the arm, the screwthreaded part, which is of smaller diameter than the oscillating spindle, being joined to the latter by a generally frustoconical bearing surface with regular splines along the generatrices of the frustum of the cone.
Existing arms have a corresponding frustoconical mounting hole which, when first fitted, is forced over the splined part of the spindle, whose splines are then imprinted into the bore of the arm, which is generally made of a metal softer than the steel of the spindle, such as a zinc-based alloy known as Zamak or an aluminum-based alloy.
The imprinting of the splines in the bore prevents the shaft rotating relative to the spindle. However, this type of assembly, although simple and inexpensive, is not very resistant to demounting and does not guarantee that the arm is perpendicular to its rotation axis, in particular where it is nested over the splined frustoconical part.
If an adjustment in its position proves necessary, clamping it again in a different angular position on the surface of the bore of the arm, which already has splines imprinted in it, will take place on top of the original splines, causing them to be chewed up, and the splines will no longer be able to transmit the drive torque for the windshield wiper arm. For this reason, automotive vehicle manufacturers scrap any windshield wiper arm that is mounted incorrectly, either on the production line or as a repair, and replace it with a new one in order to guarantee mechanical strength and to avoid a reduced locking effect and risks of deformation on the clamping surfaces that can lead to defective positioning of the arm. The quality of the assembly will depend on the care with which the arm was initially positioned on the production line.
This type of mounting on a splined frustoconical bearing surface does not accurately control the axial hi position of the arm on the spindle because, although the nature of the materials used enables the male splines on the steel spindle to be impressed into the female cone of the frustoconical bearing surface, the frustoconical shape adopted makes it difficult to maintain the assembly tension (the materials used, which are generally soft metals, having a tendency to creep), degrading the quality of the connection, and the shaft then turns within the female frustoconical bearing surface without driving the windshield wiper.
On the other hand, if the frustoconical assembly is well designed and functions correctly, it is inherently self-wedging and an extractor is required to demount it.
Moreover, with a frustoconical bearing surface, especially a short one, it is difficult to guarantee that the arm is perpendicular to its spindle. Any such defect of perpendicularity leads to malfunctions and in particular to serious variations in the intended wiping speed and to noise and vibration of the rubber windshield wiper blade.
Pressed sheet metal arm drivers give rise to other problems. Being made of steel, the marking of the frustoconical bearing surface of the driver by the splines on the spindle will be very superficial, because of the hardness of the material and the particularly small height of the bearing surface, and this will necessitate significantly increasing the assembly pressures
The subject matter of the present invention is a windshield wiper arm structure which enables precise adjustment of its angular position, combined with low cost, and which can be mounted quickly, in a single operation, with easy adjustment of the angular location of the windshield wiper arm.
According to the invention, a device for fixing a windshield wiper arm hub to the spindle with locking means for locking the arm to the spindle, a cavity formed in the hub containing means for adjusting the angular position of the arm relative to the spindle, said hub bearing on an abutment base nested over a bearing surface of the spindle, is characterized in that, the locking means being adapted to assume either a clamping position or an unclamping position, said adjustment means include a connecting ring constrained to rotate with the spindle and accommodated in said cavity of the hub with some play allowing limited relative angular movement between the connecting ring and the hub in the unclamping position of the locking means, whereas all relative movement between the connecting ring and the hub is prohibited in the clamping position of the locking means.
Advantageously, said angular play of the connecting ring inside the cavity of the hub is determined by nesting of the connecting ring along a polygonal contour.
Accordingly, the contour of the connecting ring can be integrated with the shaft to nest it directly in the complementary cavity of the hub, and the same spring means can be disposed between the shaft and the hub, which eliminates the use of a connecting ring without excessively complicating the shape of the end of the arm. A bearing surface of polygonal shape, for example hexagonal shape, will be formed directly on the shaft, that bearing surface being nested inside a corresponding cavity of the hub having the same, but slightly larger, shape to enable angular play of the arm on the shaft.
Preferably, an angular movement buffering spring member is disposed in a space between the inside of the hub and the outside of the connecting ring.
In this variant, to damp end of sweep impacts on each reversal of the direction of operation, there is provided in the space directly separating the shaft from the hub a buffer member such as a leaf spring of appropriate shape that will equally make it possible to retain the arm in its theoretical adjustment position relative to the shaft.
Advantageously, the connecting ring has a cylindrical outside contour nested inside a corresponding bore of the hub, its rotation in said bore being angularly limited by at least one radial rib able to oscillate in at least one corresponding radial housing of the hub, spring means being disposed between the radial walls of the rib and the facing radial walls of the radial housing.
In a preferred embodiment the connecting ring will have a cylindrical outside contour nested inside a corresponding bore of the hub, its rotation in that bore being angularly limited by at least one radial rib able to oscillate in a corresponding, slightly wider groove in the hub, a larger radial rib being disposed in a larger cavity of the hub, for example in the portion thereof extending along the axis of the arm, bearing buffering spring means being disposed between the radial walls of the rib and the facing radial walls of the cavity. These spring means also determine the theoretical angular location on first fitting and retain the ring, thus facilitating fitting the arm to the shaft in its theoretical centered position and holding it in position during assembly.
There will then be provided a controlled range of adjustment of the angular position of the arm, in elastic bearing engagement. Once fitted, the arm will be locked by tightening the assembly nut with the locking washer, as previously.
Preferably, a metal outer shell forms a housing around the hub.
The arm according to the invention has an end for assembly onto the spindle consisting of a composite structure characterized by an external shell, preferably of pressed sheet metal, forming a drive housing of the windshield wiper arm, which housing is open at the bottom, has a hole at the top through which the spindle passes, and receives means for locking the arm onto the spindle such as a nut with a locking washer or an assembly screw, depending on the types of assembly concerned, this housing containing a separate hub, which is made from a molded or cast material, such as a plastics material or Zamak, aluminum, magnesium, etc., is adapted to receive means for adjusting the angular position of the arm, is nested in and fastened to the housing, and has shapes complementary to those of said housing to fasten the hub into the housing and constrain them to rotate together. The hub can equally be fastened to the housing by other means such as molding, pins, crimping, clipping, or riveting.
This composite structure facilitates complex and precise shaping of the hub by molding, combined with sufficient strength, imparted by covering the housing with sheet steel, which acts as a reinforcing band on the hub and its adjustment and assembly mechanisms and provides a particularly rigid connection to the windshield wiper arm, in particular in the case of a long arm.
The simplest shape for this kind of composite hub could be applied in particular to nesting over spindles with splined frustoconical bearing surface, as in the prior art, but whose bore is extended, starting from the larger base of the frustum of the cone or from its toroidal extension, by a guide sleeve nested over the rod of the spindle and guaranteeing a perpendicular assembly. This first application thereby remedies the main defect of assemblies using spindles with splines on a frustoconical bearing surface.
A variant hub will have a frustoconical bearing surface bore whose larger base can be connected to the cylindrical rod of the spindle by a toroidal connecting surface forming a abutment and therefore improving axial location of the nested hub of the arm, which has an initially smooth surface on which the splines of the spindle will be imprinted. This strengthens the adjustment on a frustoconical bearing surface. The smooth frustoconical bearing surface of the hub has at its larger base end a rounded portion whose toroidal surface nests over and abuts against a splined toroidal surface of complementary shape extending the splines of the frustoconical bearing surface of the spindle as far as its outside diameter.
To improve the rotational interlocking of the frustoconical nesting arrangement, instead of being regularly distributed in the usual way, the splines on the frustum of the cone of the shaft could be irregularly or randomly distributed, so that at least some of them nest correctly in some of the splines imprinted on the smooth frustoconical surface of the arm when it was first fitted.
With regularly distributed splines, if the shaft is offset by one half-tooth, for example, relative to the splines imprinted in the arm, the tips of all the teeth on the shaft will face the tips of all the teeth that were imprinted in the hub during first assembly. This cannot occur with irregularly distributed splines because at least some of them will be in the correct position.
Advantageously, the arm is held perpendicular to the spindle by the abutment base, which abuts on a transverse bearing surface of the spindle.
The perpendicularity of the arm will advantageously be controlled by this abutment base, which can be made from a sintered metal, and whose central hole will have a splined surface that nests over the splined bearing surface of the spindle, said base abutting on the bottom of that bearing surface, which ensures its perpendicular and axial position relative to the spindle through a self-locking assembly with no wedging effect, as well as the perpendicularity of the hub, which bears on this abutment base, whose cylindrical surface provided with a shoulder for centering the hub closes the cavity in the hub containing the means for adjusting the angle of the arm.
To prevent creep due to crushing of the hub when it is clamped against the abutment, the flanks of the housing will have a predetermined height relative to the hub and will bear against the abutment base to maintain the required assembly pressure.
For assemblies on spindles with a cylindrical splined bearing surface, the perpendicularity of the arm thereon is controlled by a abutment base, which can be made from a sintered metal, and whose central hole has a splined surface that nests over the splined bearing surface of the spindle, said base abutting against the end of that bearing surface, which ensures its perpendicular and axial position relative to the spindle by a self-locking assembly with no wedging effect, and also the perpendicularity of the hub which bears on this abutment base, whose circular surface provided with its centering shoulder closes the cavity in the hub containing the means for adjusting the angle of the arm.
Preferably, the height of the flanks of the housing relative to the hub is such that they bear against the abutment base.
Advantageously, the shapes of the housing and the hub and the height of the flanks of the housing relative to the hub are such that the bottom and the flanks of the housing bear on the top and the flanks of the hub, respectively, said hub itself bearing on the abutment base, the flanks of the hub being splined.
Preferably, the connecting ring is constrained to rotate with the spindle by means having cooperating or complementary shapes.
Advantageously, said means having cooperating shapes consist of splines.
Preferably, said means having cooperating shapes consist of polygons, advantageously squares.
Advantageously, the means with cooperating shapes are carried directly by the connecting ring and means with cooperating shapes are carried by the spindle.
Preferably, the connecting ring is constrained to rotate with the spindle by the abutment base, the means with cooperating shapes are carried by the abutment base and means with cooperating shapes are carried by the transverse bearing surface of the spindle, complementary means, which are advantageously indexed, being provided for driving of the connecting ring by the abutment base.
Advantageously, the spindle includes a xe2x80x9cpolarizerxe2x80x9d device consisting of gaps left by missing splines and the splines of the connecting ring of the hub include polarizer splines with no gaps between them, the resulting solid members corresponding to the gaps left by the missing splines of the spindle, the abutment base including a full complement of splines.
Preferably,the radial rib has an elastic end portion adapted to bear on a portion of the corresponding wall of the radial housing.
Thus the windshield wiper arm according to the invention will be mounted on the screwthreaded end of its spindle, in a manner that is known in the art, by locking it by means of an appropriate nut and Washer in a hole of the hub at the end of the arm against a bearing abutment base fastened to the spindle, said end hub having on its locking bearing face a housing in which is nested a connecting ring constrained to rotate with the end of the spindle but free to rotate by a small amount and against a resisting spring bearing force, said assembly being characterized in that the connecting ring has at least one flexible radial rib disposed in a corresponding housing of the hub receiving the connecting ring, rotation of the windshield wiper arm relative to its spindle and the connecting ring in elastic bearing engagement being ensured by elastic flexing of said radial rib bearing against the corresponding wall of its housing.
Advantageously, the radial rib can flex elastically because it has a projecting shape at its end which alone bears on the wall of its housing and allows free flexing of the rib in the housing.
Preferably, the radial rib has at least one flexing lug.
Advantageously, the length of the flexing lugs is less than the radial depth of the housing, the base of the rib forming an abutment bearing on a portion of the corresponding wall of the housing limiting angular movement of the arm while it is being adjusted during first fitting or if it is loosened.
Advantageously, there is at least one angular movement abutment rib on the periphery of the connecting ring.
Preferably, the connecting ring is nested in the corresponding cavity of the windshield wiper arm hub with a taper.
Advantageously, the taper of the external contour of the connecting ring and the corresponding walls of the cavity of the hub is at least equal to or greater than the taper of the arm hub enabling its direct extraction from the mold.
Preferably, the locking means include a nut and a locking washer held in position on the external face of the windshield wiper arm hub by a centering bead thereon which is concentric with the exit hole for the screwthreaded end of the spindle.
Advantageously, it consists of a pre-assembled sub-assembly at the end of the windshield wiper arm including, on the one hand, a nut and a locking washer held in position on the external face of the windshield wiper arm hub by a retaining fork having two top teeth bearing on the washer on either side of the nut and two bottom teeth bearing on the abutment base on either side of the hole for fitting it over the spindle, the bottom teeth being connected by a semifrustoconical shape forming a funnel to facilitate guiding the end of the spindle into the hole in the abutment base.
Preferably, the distance from the bearing face of the connecting ring on the abutment base to the entry of the screwthread of the nut is greater than the distance between the entry of the means with complementary shapes carried by the spindle and the top of the screwthread on the shaft, so that the means with complementary shapes of the ring can be engaged over the means with complementary shapes of the spindle before tightening the nut.
Advantageously, the distance from the face of the abutment base bearing on the transverse bearing surface on the spindle to the entry of the screwthread of the nut is greater than the distance between the entry of the means with complementary shapes carried by the spindle and the top of the screwthread on the shaft so that the means with complementary shapes of the abutment base can be engaged over the means with complementary shapes of the spindle before tightening the nut.
The invention also relates to eliminating noise generated by windshield wipers due to their effectiveness varying as a function of the pressure with which they are pressed onto the windshield. The noise can be caused by poorly controlled inclination of the rubber blade relative to the surface of the windshield, to which may be added excessive pressure of the arm bearing spring. The blade then tends to jerk and cause the whole of the arm to vibrate.
The curved shape of the windshield may also vary from one supplier to another, and it can be beneficial to modify the bearing pressure by increasing the tension of the spring, rather than adding a spoiler whose aerodynamic effect would increase that bearing pressure.
According to the invention, this problem will be solved by articulating the abutment base to the spindle so that it can be adjusted, either in terms of its normal position perpendicular to its attachment spindle or offset by a positive or negative angle relative to that position.
Advantageously, the transverse bearing surface on the drive spindle over which the abutment base is nested includes at least two diametrally opposite flats, limited in the lengthwise direction by shoulder surfaces, which are concave and provided with teeth perpendicular to the spindle and parallel to each other, the abutment base being nested over the bearing surface of the spindle with a clearance enabling it to tilt relative to its normal perpendicular position, and having convex toothed bearing surfaces nesting over the concave toothed shoulder surfaces of the drive spindle, the mutual nesting of the teeth of the bearing surfaces maintaining the chosen inclination of the abutment base when it is being first fitted.
Preferably, the shoulder surfaces on the spindle and the bearing surfaces on the abutment base are segments of cylindrical surfaces of a cylinder whose axis intersects the spindle perpendicularly thereto.
Advantageously, the shoulder surfaces on the spindle and the bearing surfaces on the abutment base are sectors of a sphere whose center is on the spindle and form a ball-joint locked by the nesting of the teeth, the 90xc2x0 relative location of which enables longitudinal sliding of the nested teeth for adjusting the relative location of the perpendicular sets of teeth.
Two adjustment solutions can then be envisaged:
The simpler one, in particular during fitting on the production line, consists of adjusting only one factor at a time, either the tension or the inclination of the bearing spring of the rubber wiper blade, which will be obtained with the same spindle, the same abutment and the same adjuster ring, and therefore without modification of the components, by pivoting the orientation of the spindle 90xc2x0 relative to its drive link, as a function of the required adjustment during fitting to the vehicle, by locating the arm by means of two opposed concave and convex toothed bearing surfaces on the abutment and on the spindle.
The second solution will simultaneously make it possible to:
Adjust the bearing pressure.
Adjust the inclination of the rubber blade.
Adjust both at once.
For example, it may be beneficial to impart a positive or negative angle to the rubber blade, retaining the possibility of remaining neutral or increasing or reducing the bearing pressure.
In this case, two sets of concave toothed shoulder surfaces on the spindle and convex toothed bearing surfaces on the abutment base will be used, forming a bearing surface composed of sectors of a spherical dome centered on the spindle and enabling ball-joint type adjustment of the inclination of the abutment base, the double set of mutually nested teeth ensuring that it is retained in the chosen position.
It will be noted that this solution for adjusting the sweep position by adjusting the position of the bearing abutment base is still very simple and inexpensive, the shapes of the bearing surfaces and the teeth being easily obtained on the spindle by cold stamping and on the abutment by cold stamping or sintering.
Preferably, the spindle has four flats which impart a square section on it and over which is nested the abutment base, whose bearing base is inclined and which transmits that inclination to the connecting ring, constrained to rotate with the bearing base of the abutment base by complementary means consisting of four tongues over which it is nested, different angular locations of the connecting ring and therefore of the windshield wiper arm being obtained by modifying the relative location of the abutment base on its nesting square on the spindle by 90xc2x0 or 180xc2x0.
Advantageously, a washer is disposed between the abutment base and the base of the square on the spindle over which it is nested, the washer having on its face bearing on the abutment a concave toothed surface on which a convex toothed surface of the abutment base bears.
The play between the hub and the ring enabling the angular location to be varied by an amount of the order of several degrees, sufficient for adjusting the position of the windshield wiper, can be ensured by nesting the connecting ring in its cavity of the hub with a clearance along a contour that does not allow the ring to rotate in its cavity, such as a polygonal contour limiting the possibility of angular movement. After placing the arm in the required angular position, the stacked hub and housing will be locked in position against the abutment base by tightening the nut and its arm locking washer to the end of the spindle.
The above kind of device will advantageously consist of a pre-assembled sub-assembly at the end of the windshield wiper arm and including, on the one hand, the nut and its locking washer, held in position on the outside face of the housing, for example by locating lugs formed in the sheet metal of the housing or by a washer equipped with lugs provided with retaining claws, facing the exit hole of the screwthread end of the spindle, and, on the other hand, the assembly of the abutment base, connecting ring and locating spring clipped into the corresponding cavity of the hub, in turns fastened to the housing by studs heat-welded into corresponding holes in the sheet metal of the housing. On demounting, the nut, retained by the mounting lugs, will act as an extractor to facilitate demounting the complete sub-assembly without requiring any other tools.
When this arm sub-assembly pre-assembled in this way is fitted to the end of the shaft, the distance from the bearing face of the connecting ring on the abutment base to the entry of the splines on the shaft will advantageously be greater than the distance between the entry of the screwthread of the nut and the top of the screwthread on the shaft, so that the splines of the ring can be engaged over the shaft before tightening the nut. In this way the ring is engaged over the splines of the shaft before the nut abuts on the end of the screwthread on the shaft to retain the arm angularly on the shaft, so that the operative no longer has to hold the arm in position and therefore has both hands free to fit the second arm and adjust and lock both arms simultaneously.
On the assembly line, the operator will only have to fit this sub-assembly over the splined part of the spindle.
Advantageously, the length over which the hub of the windshield wiper arm is nested, including the length over which the combination of the abutment base and the connecting ring is engaged over the spindle, ensures retention of the hub on the spindle and bracing of the hub to press the windshield wiper blade onto the windshield.
Then the operative will only have to place the windshield wiper arm in the required position with one hand and, holding his nut driver in the other hand, tighten the nut to lock the arm in position. This will minimize assembly time and this adjustment will be repeatable subsequently under any circumstances.
To avoid errors in orienting the arm when fitting it as indicated above, a xe2x80x9cpolarizerxe2x80x9d device is provided enabling the hub of the arm to be mounted on the splines of the shaft in only one position. To this end, the shaft has splines missing, leaving gaps, which enables the abutment, with a fill complement of splines, to be fitted in any orientation, which facilitates assembly, although the connecting ring of the hub of the arm includes polarizer splines with no gaps between them, the resulting solid members corresponding to the gaps because of the missing splines on the spindle, as a result of which the connecting ring can be mounted in only one indexing position, the only theoretically required position, from which the orientation of the arm can be finally adjusted at the level of the angular abutments of the connecting ring in their larger cavities provided with spring means formed in the hub of the arm, as previously described.
This embodiment of a windshield wiper arm structure offers secure positioning of the arm on its spindle, including after demounting, and enables a precise angular position adjustment, if necessary, whilst still being of low cost and compatible with existing mounting spindles, on which this arm will be mounted on vehicle assembly lines by a simple and fast assembly operation less dependent on the human factor, with possible easy adjustment of the angular location of the windshield wiper arm.
The elastic flexing of the radial rib will advantageously be procured by providing a projecting shape such as a bead at its end, that alone will bear on the wall of its housing and allow free flexing of the rib in that housing. To combine flexibility for flexing with sufficient mechanical strength, the radial rib will consist of a plurality of parallel flexing lugs having the same flexing flexibility but whose resistances to flexing will be additive. These lugs could be shorter than the rib, whose more solid base will then form an abutment limiting the angular displacement of the arm during its adjustment on fitting. One or more small solid ribs can also be provided on the periphery of the connecting ring, depending on the required strength, providing this angular displacement limiting abutment function. Considerable adaptability of the assembly structure is therefore obtained by appropriately dimensioning the connecting ring and its rib or ribs.
In this kind of configuration the connecting ring must reconcile the requirements of material flexibility, enabling elastic deformation in flexing of the radial rib, and sufficient mechanical strength of the splines in its bore, which have to be nested over the corresponding splines on the spindle. According to another feature of the invention, the nesting of the connecting ring in the corresponding cavity of the hub will include a taper.
In addition to its conventional function of facilitating molding, that taper will have the result, during locking of the arm on the spindle, compressing the connecting ring in its housing, of exerting a component of pressure perpendicular to the spindle resulting in an effect of banding the connecting ring onto the spindle, which significantly reinforces the splined 1 assembly. Moreover, this taper prevents complication of the tooling for pressure casting the arm, by the provision of demountable parts, if the arm has a skewed shape necessitating a mold extraction plane inclined relative to the spindle. Tapering the outside contour of the connecting ring and the corresponding walls of its housing at an angle at least equal to or greater than that inclination will enable direct extraction of the arm from the mold without adding supplementary mobile members in the mold.
Accordingly, by a dimensional adjustment of the connecting ring as a function of the material chosen and operating constraints, fixing the windshield wiper arm according to the invention will enable easy adaptation to all types of windshield wiper, at moderate cost.
Clearly, the invention:
ensures that the windshield wiper is driven securely, even if the clamping is inadequate,
provides an incompressible mounting in which the assembly tension is maintained by compression spring means,
achieves a perfectly perpendicular and precise axial position of the arm on its spindle,
transmits high drive torques and is more rigid than existing arms,
can be demounted without special tools and replaced quickly and securely in the same position without any possibility of error and as many times as may be necessary throughout the service life of the vehicle,
enables the three adjustments provided (sweep, twist, blade pressure) to be modified without demounting any component, including the clamping nut and its washer,
does not necessitate any modification to existing fabrication techniques and improves the method of mounting the windshield wiper arm on the production line,
enables the windshield wiper arm to remain in its theoretical position on the spindle of its own accord, before tightening the nut, so that the operative has his hands free, and
can be mounted interchangeably on the main spindle diameters already in use.

Device for fixing the hub of an arm of a windscreen wiper

Societe de Recherches d""Etudes et de Valorisation


Aspects of this invention relate to an adjustable bed that may include one or more articulating portions, and may include one or more components, including an air inflatable mattress associated with the adjustable bed frame, a programmable logic controller, a remote memory storage facility, a remote storage location of user preferences, a cell phone remote control, a modular control device, an air purification facility, a power outlet controller, a Bluetooth remote control, an ultra wide band remote control, a wireless USB remote control, and the like.

1. Field
This invention relates to an adjustable bed.
2. Background
Adjustable beds may contain at least one section of which a user may control the position. The user may typically adjust the bed by using a control to move the adjustable section in its direction of movement. Additionally, the adjustable bed may include various types of mattresses and vibration of sections. Often, users that have adjustable beds because a medical issue may require certain positions to aid recovery, positioning to relieve discomfort as a result of pain, or the like. These users may, because of these issues, spend significant amount of time in the adjustable beds, some users may be confined to bed.
Many existing adjustable beds may provide the basic requirements of moving bed sections to positions that are required by a user, but do not account for controlling other devices that may be beneficial to the user and provide for a level of independence to the user.
A typical adjustable bed may consist of a wood decking for each of the sections of the bed connected together with hinges to allow the various positions between the sections. There are actuators connected between the bed frame and the wood decking for moving the adjustable sections into user-desired positions. The adjustable bed may have a "wall hugging" feature that maintains a consistent distance between the mattress and the wall as the bed is adjusted. Some adjustable beds may use wooden or plastic slats to support the mattress instead of a solid wood platform.
The adjustable bed may have at least one actuator to position the adjustable bed sections. In some cases there is one actuator to position more than one, such as positioning both the thigh and foot sections with one actuator. There may also be more than one actuator for each adjustable section.
Hospitals have used adjustable beds for many years to provide comfortable and medical required positions.
A need exists for an adjustable bed that provides for the adjustable function required in an adjustable bed and provides for control of additional devices, a plurality of different bed section actuator types and movable memory types that may provide independent activities to the user of the adjustable bed.

This patent is subject to a terminal disclaimer.


A lock structure including an activation device, a combination lock, and a setting device is provided. The combination lock has a plurality of dials, a shaft passing through the dials, and a plurality of first gears disposed on one side of each dial. Each first gear further includes a missing tooth. One end of the shaft is connected to the activation device. The setting device has a plurality of second gears corresponding to the first gears and a setting shaft, wherein one end of the setting shaft passes through the second gears and the other end is connected to the activation device. When the activation device is activated, the second gears are driven to rotate the first gears, so that when each second gear runs free with the missing tooth of each first gear, the dials are in a predetermined position. That is, by means of the activation device and the setting device, the dials of the combination lock can automatically return to the predetermined position after opening or closing the lock.

1. Field of the Invention
The present invention relates to an auto reset device. More particularly, the present invention relates to a dial combination lock structure with auto-reset function wherein the dials can automatically return to a predetermined position after opening or closing the lock.
2. Description of the Prior Art
With the advancement of technology, a variety of locks are developed. Locks are specifically developed for different applications and purposes, for example, in order to protect articles, displayed or temporarily stored in glass showcases, shop windows, or deposit cabinets in markets, schools or other public places, from being stolen or taken away.
Most of currently available locks for use in the public places are a key lock or a combination lock disposed separately. In the case of using the key lock, it is very inconvenient for the user to keep the key in a proper place. Moreover, there is always a risk of losing the key. Therefore, the combination lock is more often used in the public places, such as markets, supermarkets, stores, public baths, dining halls, campuses, or other similar public places. When the combination lock is used in a public cabinet, the user only needs to set a password of the combination lock and unlocks the combination lock by turning the dials.
During the operation, when a new password of the combination lock is set by the user after his/her personal stuffs are put into the deposit cabinet, the user has to purposely mess up the dials of the combination lock to prevent the password from being revealed before leaving the deposit cabinet. Otherwise, the personal stuffs would be very possible to be stolen. Therefore, in order to overcome the above problems, improve convenience and safety, and achieve other purposes, a lock structure with auto-reset function is desired.


The invention relates to crosslinked bead polymers doped with superparamagnetic iron oxide, to a process for the preparation of the bead polymers, and to the use thereof in nucleic acid diagnosis.

The invention relates to crosslinked bead polymers doped with superparamagnetic iron oxide, to a process for the preparation of the bead polymers, and to the use thereof in nucleic acid diagnosis.
So-called genetic diagnosis has become increasingly important recently.
Genetic diagnosis has become involved in the diagnosis of human diseases (inter alia detection of pathogens, detection of genome mutations, discovery of circulating tumour cells and identification of risk factors for predisposition to a disease). However, genetic diagnosis is also now finding applications in veterinary medicine, environmental analysis and food testing. A further area of application comprises investigations in institutes of pathology/cytology or within the framework of forensic problems. However, genetic diagnosis is now employed also for the purposes of quality control (for example investigations of blood samples for freedom from pathogens), and legislation is planned to regulate such tests by law in future. Methods also employed in genetic diagnosis (such as, for example, hybridization and amplification techniques such as PCR, bDNA or NASBA technology) are also among the routine methods in fundamental scientific studies.
An important step in genetic diagnosis is the obtaining of gene samples from biological material such as cells, blood, serum or urine.
EP 0 707 077 describes a method for isolating nucleic acids from biological material using soluble, weakly basic polymer. In this method, a precipitation product is generated from the soluble, weakly basic polymer and the nucleic acid in an acidic pH range, the precipitation product is separated from the unprecipitated constituents of the biological material, and washed, and the nucleic acid is liberated again from the precipitation product by adjusting a basic pH.
One disadvantage of the method in EP 0 707 077 is that the manipulation, in particular the separation and purification of the precipitation product, is difficult and very time consuming. This method can moreover be carried out using automatic analysers only under difficult conditions or not at all.
U.S. Pat. No. 4,339,337 and U.S. Pat. No. 5,356,713 describe methods for preparing magnetic beads of vinylaromatic polymer using magnetic particles. These bead polymers do not, however, contain any functional groups for attaching nucleic acids. In addition, the beads show a marked residual magnetism (remanence), which impedes dispersability thereof.
WO 8303920 describes a method for preparing magnetic polymer particles in which polymer particles are treated with solutions of, for example, iron salt, the iron being precipitated in the form of iron hydroxide. In this method, the precipitated iron compound is present both in the polymer particles and on the surface of the polymer particles. The iron compound on the surface may interfere with some applications, for example amplification of nucleic acids by Taqman PCR.
U.S. Pat. No. 5,206,159 discloses a process for preparing superparamagnetic polyacrylamide carriers. These carriers are, however, unsuitable for removing nucleic acids.
U.S. Pat. No. 5,705,628 discloses a method for binding DNA to magnetic microparticles. The magnetic microparticles preferably have a particle size of 1 xcexcm and have a surface coated with carboxyl groups. In order to achieve binding of the DNA to the particles it is necessary to use a specific salt concentration and add polyethylene glycol in a defined concentration and with specific molecular weight.
It has now been found that certain crosslinked bead polymers doped with superparamagnetic iron oxide and containing basic amino groups are outstandingly suitable for direct and automated isolation of nucleic acids.
The invention relates to crosslinked bead polymers doped with superparamagnetic iron oxide and containing basic amino groups, which are characterized in that the bead polymers contain copolymerized units of hydrophilic (meth)acrylate and amino (meth)acrylates.
The term (meth)acrylate means the derivatives of acrylic acid and methacrylic acid.
Hydrophilic (meth)acrylates are those whose homopolymers have a solubility of more than 2.5% in water at 25xc2x0 C. Examples which may be mentioned are: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, glycerol monomethacrylate, acrylamide, methacrylamide and N,N-dimethylacrylamide. Acrylamide is preferred.
Amino (meth)acrylates for the purpose of the present invention are derivatives of acrylic acid and methacrylic acid with, preferably, secondary and tertiary amino groups. The amino groups may also be part of a cycloaliphatic or aromatic ring. Suitable amino (meth)acrylates are, for example, N-(3-aminopropyl)methacrylamide, N-(3-imidazolylpropyl)methacrylamide, N-(2-imidazolylethyl)methacrylamide, N-(3-aminopropyl)acrylamide, N-(3-imidazolylpropyl)acrylamide, N-(2-imidazolylethyl)acrylamide, N-(1,1-dimethyl-3-imidazolylpropyl)methacrylamide, N-(1,1-dimethyl-3-imidazoylpropyl)acrylamide, N-(3-benzimidazolylpropyl)-methacrylamide and (3-benzimidazolylpropyl)acrylamide. Preferred amino (meth)acrylates are aminoalkyl (meth)acrylates such as, for example, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylate, N,N-dimethylaminoethyl acrylate, and N-tert-butylaminopropyl methacrylate. N,N-Dimethylaminoethyl methacrylate and N,N-dimethylaminopropyl methacrylate are particularly preferred. The amino groups in the bead polymers according to the invention may be wholly or partly in protonated form, for example as hydrochlorides.
Suitable crosslinkers are: ethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, pentaerythritol dimethacrylate, glycerol 1,2-dimethacrylate, glycerol 1,3-dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, ethylene glycol diacrylate, butanediol diacrylate, pentaerythritol diacrylate, glycerol 1,3-diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, allyl methacrylate, allyl acrylate, diethylene glycol divinyl ether and methylene-N,Nxe2x80x2-bisacrylamide. Methylene-N,Nxe2x80x2-bisacrylamide is preferred.
The amount of hydrophilic (meth)acrylate is 30 to 89% by weight, preferably 40 to 75% by weight, the amount of amino (meth)acrylates is 10 to 69% by weight, preferably 20 to 50% by weight, and the amount of crosslinker is 1 to 25% by weight, in each case based on the total of hydrophilic (meth)acrylate, amino (meth)acrylates and crosslinker.
The content of iron oxide in the superparamagnetic bead polymers according to the invention is 2 to 80% by weight, preferably 4 to 50% by weight, particularly preferably 5 to 35% by weight, based on the weight of the unswollen bead polymers.
The bead polymers according to the invention are superparamagnetic, that is to say they have a low residual magnetization (remanence) and a small coercivity. Their magnetic saturation is high, and they are strongly attracted by an inhomogeneous magnetic field. After the magnetic field has been switched off, they can be dispersed easily and completely in water or aqueous buffer solutions.
The particle size of these superparamagnetic bead polymers according to the invention is 1 to 200 xcexcm, preferably 5 to 100, particularly preferably 10 to 50 xcexcm. Microscopic image analysis is very suitable for determining the average particle size (Ø) and the particle size distribution.
As a measure of the breadth of the particle size distribution of the bead polymers, the ratio is formed from the average of the volume distribution (Dv) and the average of the number distribution (Dz). Narrow particle size distributions for the purpose of the invention mean Dv/Dzxe2x89xa62.5, preferably Dv/Dzxe2x89xa62, particularly preferably Dv/Dzxe2x89xa61.5. It has been found that bead polymers according to the invention with a narrow particle size distribution are particularly suitable for isolating nucleic acids and provide results with particularly good reproducibility in amplification methods on the surface of the bead polymers.
The bead polymers according to the invention are swellable in water. They have a swelling index of 1.25 to 8, preferably 2 to 6 (measured at 25xc2x0 C.). The swelling index is defined as the quotient of the volume of the swollen bead polymer and the volume of the unswollen bead polymer.
For experimental determination of the swelling index, 10 ml of dried, screened bead polymer are weighed into a 100 ml graduated cylinder. The quotient of the volume of the bed (V0) and the weighed amount (m) is the bulk volume (Vbulk). The graduated cylinder is made up to 100 ml with water and left to stand at 25xc2x0 C. for 10 to 20 h. During this, it is shaken occasionally and it is ensured that any air bubbles appearing can escape. The volume of the swollen bed is read off and gives V1. The quotient of V1 and V0 is the swelling index.
The present invention further relates to a process for preparing crosslinked bead polymers, which is characterized in that a monomer mixture of hydrophilic (meth)acrylate, amino (meth)acrylate, crosslinker and, where appropriate, other monomer is polymerized to beads by inverse suspension polymerization, and the latter are then doped with superparamagnetic iron oxide by an after-treatment with iron salt solution.
Inverse suspension polymerization means for the purpose of the invention a process in which the monomer mixture of hydrophilic (meth)acrylate, amino (meth)acrylate, crosslinker and, where appropriate, other monomer is activated with a free-radical former which is soluble in the monomer mixture, and the activated monomer mixture is emulsified with addition of a dispersing aid in a nonaqueous solvent to give droplets, and then the droplets which have formed are cured by raising the temperature.
The hydrophilic (meth)acrylate, the amino (meth)acrylate and the crosslinker correspond to the compounds mentioned above. The amino (meth)acrylate can moreover advantageously be employed at least partly in the ammonium form, for example as hydrochloride. Suitable as other monomer are, for example, N-vinylpyrrolidone, vinylimidazole, styrene, alpha-methylstyrene, chloromethylstyrene, acrylonitrile, vinyl acetate and maleic anhydride, in amounts of up to about 25% by weight based on the complete mixture of monomers. It is beneficial to dilute the monomer mixture with water or water/alcohol mixtures. Suitable amounts of diluent are, for example, 10 to 200% by weight, preferably 50 to 150% by weight, based on the monomer mixture.
Suitable free-radical formers are azo compounds and peroxy compounds. When water is used as diluent, potassium peroxodisulphate and sodium peroxodisulphate are very suitable, also in combination with bisulphite or hydrogen sulphite. Other preferred free-radical formers are the azo compounds such as 2,2xe2x80x2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and 2,2xe2x80x2-azobis(2-amidinopropane) dihydrochloride. The free-radical former is used in amounts of 0.02 to 2.5% by weight, preferably of 0.1 to 1% by weight, based on the complete mixture of monomers.
Suitable as nonaqueous solvents for the purpose of the present invention are primarily hydrocarbons and halogenated hydrocarbons, and low-viscosity silicone oils. Preference is given to linear, branched and cyclic aliphatic hydrocarbons. Examples which may be mentioned are hexane, heptane, n-octane, isooctane, isododecane and cyclohexane. It is, of course, also possible to use mixtures of different hydrocarbons.
Suitable dispersing aids are oil-soluble polymers with a molecular weight of 2 000 to 1 000 000. Preference is given to polymers containing copolymerized units of C6- to C22-alkyl (meth)acrylates and/or vinyl ester of C6- to C22-carboxylic acids. Examples which may be mentioned are polymers with copolymerized units of stearyl methacrylate, lauryl methacrylate and vinyl stearate. Copolymers of C6- to C22-alkyl (meth)acrylates and vinyl ester of C6- to C22-carboxylic acids and hydrophilic monomers are particularly suitable. Hydrophilic monomers mean in this connection polymerizable olefinically unsaturated compounds which are wholly or partly (more than 2.5% by weight at 20xc2x0 C.) soluble in water. Examples which may be mentioned are: acrylic acid and its alkali metal and ammonium salts, methacrylic acid and its alkali metal and ammonium salts, hydroxyethyl methacrylate, hydroxyethyl acrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, triethylene glycol monoacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monoacrylate, tetraethylene glycol monomethacrylate, glycerol monoacrylate, aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, acrylamide, methacrylamide, vinylpyrrolidone and vinylimidazole. Preference is given to hydroxyethyl methacrylate, aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, acrylamide, methacrylamide, vinylpyrrolidone and vinylimidazole.
Particularly preferred dispersing aids are copolymers of
The amount of the dispersing aid employed is generally 0.1 to 8, preferably 0.5 to 5, % by weight, based on the nonaqueous solvent.
The stirring speed during the polymerization is important for adjusting the particle size. In the process according to the invention, the size of the bead polymers obtained decreases as the stirrer speed increases. The exact stirrer speed to adjust to a particular predetermined bead size depends in the individual case greatly on the size of the reactor, the geometry of the reactor and the geometry of the stirrer. It has proved to be expedient to find the stirrer speed necessary by experiment. For laboratory reactors with a reaction volume of 0.51 and equipped with a gate stirrer, in general bead diameters of 10 to 25 xcexcm are obtained on use of copolymers of methacrylic acid C13-ester and hydroxyethyl methacrylate as dispersing aid with speeds of 800 to 1 000 rpm.
The polymerization temperature depends on the decomposition temperature of the initiator employed and on the boiling point of the nonaqueous solvent. It is generally between 50 and 150xc2x0 C., preferably between 55 and 100xc2x0 C. The polymerization takes 0.5 to some hours (for example 10 hours).
After the polymerization it is possible for the polymer to be isolated by conventional methods, for example by filtration or decantation, and, where appropriate after one or more washing steps, be dried. It is possible to fractionate the resulting bead polymer by physical methods in order to adjust to a narrower particle size distribution. Suitable fractionation methods are, for example, screening, sedimentation and air classification.
The after-treatment for doping with superparamagnetic iron oxide takes place with mixtures of aqueous Fe2+ and Fe3+ salt solutions. The corresponding chlorides are very suitable. The Fe2+:Fe3+ molar ratio should in this case be 2:1 to 1:2. It is moreover possible to start from iron salt solutions with a different Fe2+:Fe3+ ratio and to effect the optimal Fe2+:Fe3+ ratio by using oxidizing or reducing agents. Examples of oxidizing agents are peroxo and nitro compounds, and an example of a suitable reducing agent is sodium bisulphite. The concentration of the iron salt solutions is generally 10 to 50% by weight, preferably 20 to 40% by weight.
The iron salt solution is preferably brought into contact with dry, anhydrous bead polymer. It is particularly advantageous in this connection if the bead polymer swells by taking up the entire iron salt solution; and no excess iron salt solution remains in the interstices of the beads or on the surface of the beads.
The iron salts taken up by the swollen bead polymer are converted into the corresponding iron hydroxides by adding bases. Alkaline solutions of sodium hydroxide, sodium carbonate or ammonia are very suitable. Ammonia is preferred because an excess can easily be removed by evaporation. Ammonium salts formed are removed by thorough washing with water.
The iron hydroxide is converted into iron oxide (dehydrated) by heating the bead polymer. The heat treatment in this case can take place in a simple manner in aqueous suspension at 65 to 100xc2x0 C. Suitable heating times are 0.5 to 5 hours. The conversion of the iron hydroxide into iron oxide is evident from the change in colour from pale brown to dark brown or black. The bead polymer is then removed and dried.
If required, the dried bead polymers doped with superparamagnetic iron oxide obtained in this way can be treated once more in the manner described above, in which case the content of superparamagnetic iron oxide is increased. It is possible in this way to set iron oxide contents of more than 50% by weight.
The present invention further relates to a process for isolating nucleic acids from a sample, comprising the following steps
A) mixing the sample with a bead polymer at a pH of 7 or below, the nucleic acids being adsorbed,
B) removing the bead polymer including the adsorbed nucleic acids using a magnetic field and
C) mixing the bead polymer with an aqueous phase with a pH above 7, the adsorbed nucleic acids being released,
which is characterized in that the bead polymer is doped with superparamagnetic iron oxide, and contains copolymerized units of hydrophilic (meth)acrylate and amino (meth)acrylates.
The process according to the invention is suitable for isolating and/or purifying nucleic acids of various origins, for example from cells, tissue materials, blood or pathogens. Before isolating the nucleic acids, the material to be investigated is disrupted by techniques known per se, such as, for example, disruption by protease digestion, resulting in a sample suitable for subsequent steps A to C, a lysate. Where appropriate, the biological material is lysed in a step inserted after process step A). Other suitable disruption methods have been described in DE-A-4 333 805.
The sample is mixed with the bead polymer according to the invention at a pH of 7 or below, preferably in the range from 2 to 6, particularly preferably in the range from 2 to 3, at room temperature. The bead polymer is removed with the aid of a magnetic field. The complex of nucleic acid and bead polymer obtained in this way can then be purified by washing with suitable buffers.
To liberate the bound nucleic acids from the complex, the pH of the complex is then adjusted to pH values above 7, preferably from 8 to 14, particularly preferably in the range 12 to 14.
The bead polymers according to the invention provide higher adsorption and release rates than the soluble polymers disclosed in EP-A-0 707 077. Isolation can be carried out more easily, that is to say with fewer steps and in shorter times. The purity of the isolated nucleic acids is higher and, in particular, they contain fewer inhibiting by-products, so that amplification of the nucleic acids, for example, the so-called xe2x80x9cPCRxe2x80x9d and the xe2x80x9cRT-PCRxe2x80x9d takes place particularly well. The process according to the invention is also superior to the method described in EP-A-0 707 077 in relation to restriction enzyme digestion of the nucleic acids obtained.
The bead polymers according to the invention are also very suitable for amplifying the adsorbed nucleic acids for example by the so-called xe2x80x9cTaqman PCRxe2x80x9d directly on the bead polymers (that is to say without step C).


A lithographic projection apparatus includes, a radiation system for supplying a projection beam of radiation, a mask table provided with a mask holder for holding a mask, a substrate table provided with a substrate holder for holding a substrate, a projection system for imaging an irradiated portion of the mask onto a target portion of the substrate, wherein the substrate holder has a supporting face for supporting a substrate and the supporting face is at least partially coated with a layer of electrically conductive material.

1. Field of the Invention
The invention relates to a lithographic projection apparatus comprising:
a radiation system for supplying a projection beam of radiation;
a mask table provided with a mask holder for holding a mask;
a substrate table provided with a substrate holder for holding a substrate;
a projection system for imaging an irradiated portion of the mask onto a target portion of the substrate,
the substrate holder having a supporting face for supporting a substrate.
2. Discussion of the Related Art
An apparatus of this type can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, the mask (reticle) may contain a circuit pattern corresponding to an individual layer of the IC, and this pattern can then be imaged onto a target area (die) on a substrate (silicon wafer) which has been coated with a layer of radiation-sensitive material (resist). In general, a single wafer will contain a whole network of adjacent dies which are successively irradiated through the reticle, one at a time. In one type of lithographic projection apparatus, each die is irradiated by exposing the entire reticle pattern onto the die at once; such an apparatus is commonly referred to as a waferstepper. In an alternative apparatusxe2x80x94which is commonly referred to as a step-and-scan apparatusxe2x80x94each die is irradiated by progressively scanning the reticle pattern under the projection beam in a given reference direction (the xe2x80x9cscanningxe2x80x9d direction) while synchronously scanning the wafer table parallel or anti-parallel to this direction; since, in general, the projection system will have a magnification factor M (generally  less than 1), the speed v at which the wafer table is scanned will be a factor M times that at which the reticle table is scanned. More information with regard to lithographic devices as here described can be gleaned from International Patent Application WO 97/33205.
Up to very recently, apparatus of this type contained a single mask table and a single substrate table. However, machines are now becoming available in which there are at least two independently movable substrate tables; see, for example, the multi-stage apparatus described in International Patent Applications WO 98/28665 and WO 98/40791. The basic operating principle behind such multi-stage apparatus is that, while a first substrate table is underneath the projection system so as to allow exposure of a first substrate located on that table, a second substrate table can run to a loading position, discharge an exposed substrate, pick up a new substrate, perform some initial alignment measurements on the new substrate, and then stand by to transfer this new substrate to the exposure position underneath the projection system as soon as exposure of the first substrate is completed, whence the cycle repeats itself; in this manner, it is possible to achieve a substantially increased machine throughput, which in turn improves the cost of ownership of the machine.
Lithographic apparatus may employ various types of projection radiation, such as ultra-violet light (UV), extreme UV, X-rays, ion beams or electron beams, for example. Depending on the type of radiation used and the particular design requirements of the apparatus, the projection system may be refractive, reflective or catadioptric, for example, and may comprise vitreous components, grazing-incidence mirrors, selective multi-layer coatings, magnetic and/or electrostatic field lenses, etc; for simplicity, such components may loosely referred to in this text, either singly or collectively, as a xe2x80x9clensxe2x80x9d. The apparatus may comprise components which are operated in vacuum, and are correspondingly vacuum-compatible. As mentioned in the previous paragraph, the apparatus may have more than one substrate table and/or mask table.
In many applications, the supporting face of the substrate holder comprises an underlying surface which is provided with a matrix arrangement of protrusions, each protrusion having an extremity remote from the underlying surface and being embodied such that these extremities all lie within a single substantially flat plane. Further, the substrate holder generally comprises a vacuum wall that protrudes from the underlying surface, encloses the matrix arrangement, and has a substantially uniform height. The underlying surface inside the wall is typically provided with at least one aperture extending through the substrate holder and through which the area enclosed by the wall can be accessed, so as to allow it to be at least partially evacuated. Such evacuation causes a substrate placed on the supporting surface to be sucked against the protrusions, whereby the substrate can be rigidly held in place.
Due to the highly stringent demands placed on the substrate table with regard to its mechanical and thermal stability, the table is generally made of a ceramic or vitreous material. An example of a suitable material in this context is ZERODUR, which is market by SCHOTT and which is predominantly comprised of a mixture of SiO2 and Al2O3, with the additional presence of various other metal oxides.
It is an object of the invention to provide a lithographic projection apparatus having an improved substrate holder.
This and other objects are achieved in an apparatus as specified in the opening paragraph, characterized in that the said supporting face is at least partially coated with a layer of electrically conductive material.
In experiments leading to the invention, the inventors conducted tests using a vitreous substrate holder and a selection of semiconductor wafers as substrates. In many cases, it was found that the wafers had the annoying habit of sticking to the substrate holder, so that they could not readily be removed after relaxation of the wafer-retaining vacuum.
Forced removal of such wafers from the substrate holder often resulted in damage to the wafer and/or the finely machined supporting face of the substrate holder, which is unacceptable in most applications.
Further analysis showed that this annoying phenomenon was only occurring for so-called backside-polished wafers, i.e. wafers which are polished to optical surface quality on both major surfaces. Initially, it was thought that the sticking might be due to the phenomenon of xe2x80x9cAnsprengenxe2x80x9d (also called Van der Waals bonding, or atomic bonding), or to the creation of a static vacuum. However, after much additional investigation, it was speculated that what was actually being observed was an electrostatic effect, whereby the wafer and the supporting face were developing opposite electrical charges, and attracting each other via Coulomb forces. In the case of conventional (i.e. xe2x80x9cone-sidedxe2x80x9d) wafers, such Coulomb forces (which decrease rapidly as a function of distance) would be relatively weak, since the natural surface roughness of the wafer""s backside would force a relatively significant separation of the wafer and the supporting face. However, in the case of backside-polished wafers, the optical polishing of the wafer""s backside allows much more intimate contact between the wafer and the supporting face, and this significantly reduced separation would lead to a greatly increased Coulomb attraction.
To test this idea, the inventors vapor-deposited a thin layer of chromium on the supporting face of the test substrate holder. In subsequent experiments with this Cr-coated substrate holder, the phenomenon of sticking wafers as described above was observed to be completely absent. The inventors thus concluded that the said phenomenon was indeed due to tribo-electrical effects, due for example to minor wafer/holder relative motion during placement of the wafer on the holder. In accordance with the present invention, any charge separation at the interface between the wafer and the supporting surface as a result of such tribo-electrical effects is effectively blocked since the electrically conductive layer keeps the (electrically conductive) wafer backside and the supporting surface at the same electrical potential.
According to the invention, the layer of electrically conductive material deposited on the supporting face of the substrate holder need not be very thick; for example, a layer with a thickness of the order of about 100-300 nm is observed to give good results. Furthermore, the conductive layer does not need to be comprised of Cr; in principle, many different metals can be used, such as Al, Pt and Au, for example, and both elemental metals and alloys may be employed. Use of a conductive polymer instead of a metal is also possible, as is the use of a conductive inorganic compound such as CrN or TiN, for example. In any case, the choice of conductive material will be determined inter alia by the demands of durability and substrate-purity in a particular manufacturing application. The skilled artisan will appreciate that such layers can be provided by many different methods, including such techniques as sputter deposition, MBE and CVD, in the case of metals and inorganic compounds, and spin-coating, spraying and CVD, in the case of conductive polymers. Best results are obtained if the conductive layer covers a substantial area of the supporting face, and ideally a majority of the area or the entire area is thus covered.
In a particular embodiment of the invention, the conductive layer is at least partially overlaid by a dielectric film. This dielectric film should be so thin as to allow significant electrical conduction in a direction perpendicular to the film; e.g. a thickness of the order of about 20-70 nm will generally be satisfactory. Such a dielectric coating can help to improve the durability of the conductive layer underneath, and also combats substrate contamination by the material of the conductive layer. A suitable example of a dielectric material for this purpose is SiOx (silica, including quartz), though other materials may also be employed in particular applications, such as Al2O3 or SiN, for example.
The invention also relates to a device manufacturing method comprising the steps of:
providing a substrate which is at least partially covered by a layer of radiation-sensitive material;
providing a mask which contains a pattern;
using a projection beam of radiation to project an image of at least part of the mask pattern onto a target area of the layer of radiation-sensitive material.
According to the invention, such a method is characterized in that during the projection step, the substrate is supported on a supporting face of a substrate holder, said supporting face being at least partially coated with a layer of electrically conductive material.
In a manufacturing process using a lithographic projection apparatus according to the invention, a pattern in a mask is imaged onto a substrate which is at least partially covered by a layer of radiation-sensitive material (resist). Prior to this imaging step, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures, such as a post-exposure bake (PEB), development, a hard bake and measurement/inspection of the imaged features. This array of procedures is used as a basis to pattern an individual layer of a device, e.g. an IC. Such a patterned layer may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, chemo-mechanical polishing, etc., all intended to finish off an individual layer. If several layers are required, then the whole procedure, or a variant thereof, will have to be repeated for each new layer. Eventually, an array of devices will be present on the substrate (wafer). These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc. Further information regarding such processes can be obtained, for example, from the book xe2x80x9cMicrochip Fabrication: A Practical Guide to Semiconductor Processingxe2x80x9d, Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN 0-07-067250-4.
Although specific reference has been made hereabove to the use of the apparatus according to the invention in the manufacture of ICs, it should be explicitly understood that such an apparatus has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms xe2x80x9creticlexe2x80x9d, xe2x80x9cwaferxe2x80x9d or xe2x80x9cdiexe2x80x9d in this text should be considered as being replaced by the more general terms xe2x80x9cmaskxe2x80x9d, xe2x80x9csubstratexe2x80x9d and xe2x80x9ctarget areaxe2x80x9d, respectively.