Height-adjustable foot arrangement

To adapt a housing (2) to an uneven standing surface, an adjustment device (1) has a foot piece (3) with an internal thread (5) that defines a displacement axis (4). The foot piece is located in a recess (6) of the housing that is accessed from a surface of the housing that faces towards the standing surface. A cross-sectional profile of the foot piece perpendicular to the displacement axis coacts with the recess to prevent rotation of the foot piece about the displacement axis. A spindle (7) with an external thread (8) that cooperates with the internal thread of the foot piece allows axial movement of the spindle along the displacement axis. A levelling wheel (9), connected to the spindle by a rotation-blocking connection allows the spindle to be rotated relative to the foot piece.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to benefit of a right of priority from European application 14186070.0, filed on 24 Sep. 2014, which is incorporated by reference as if fully recited herein.

TECHNICAL FIELD

The invention concerns an adjustment device to adapt a housing to uneven support surfaces.

BACKGROUND

Many instruments, in particular balances, automatic titrators, automatic moisture analyzers and the like have to be set up in a horizontal position in order to function properly. In the case of balances, the horizontal position is necessary to prevent the weighing object on the balance from sliding off, to ensure that the weight force is directed perpendicular to the weighing 00pan, and to thereby achieve a more accurate weighing result.

In many cases, the instrument is equipped for this purpose with a plurality of adjustable feet, whereby the distance from the support surface to the underside of the instrument can be changed for the purpose of levelling the instrument.

In order to adjust this distance for example in accordance with U.S. Pat. No. 4,219,089 A or U.S. Pat. No. 6,407,351 B1, the adjustable foot has to be relieved of the weight of the instrument, which means that the instrument has to be lifted slightly off the support surface. This is so because the adjustable foot is configured as a screw that has to be turned into or out of the instrument against the increased resistance that is caused by friction if the foot is in contact with the standing surface. As a result, the levelling of the instrument becomes more difficult, as this procedure is inaccurate and hard to reproduce.

This problem is addressed for example in U.S. Pat. No. 5,332,182 A, which discloses an adjustment device that allows the height to be adjusted from outside the balance housing. By turning a knurled nut, a spindle is moved in the direction of the axis of rotation. A plate prevents the spindle from turning along with the knurled nut and in addition clamps the knurled nut between itself and the housing. The spindle is constrained against rotation by a flattened portion of its circumference and by a passage opening in the plate whose contour matches the cross-section of the spindle. A drawback of this arrangement is the amount of space needed, which is determined by the fully retracted spindle and its adjustable length.

The adjustment device of U.S. Pat. No. 5,332,182 A is easy to operate. The knurled nut protrudes over about a fourth of its circumference to the outside through a slot in the balance housing. Thus the height-adjustment device can be arranged in the interior of the balance housing while the adjustment can be performed from the outside. This is on the one hand a desirable trait, but on the other hand the adjustment device is not secured against inadvertent changes of the adjustment setting. However, in certain situations there may be a need to secure the adjustment device or to protect its setting against being inadvertently changed, as could happen for example in a quick manual cleaning around the balance with a dust rag.

A further disadvantage of the adjustment device of U.S. Pat. No. 5,332,182 A becomes evident when the device is examined with a view to sanitary standards. For example, open screw threads are not acceptable, as the threads may fill up with deposits which can breed germs. In addition, under a so-called “wash-down” standard, a surface radius of at least 3 mm is required. The “wash-down” standard applies to equipment which is suitable to withstand industrial cleaning by spraying with water and/or cleaning agents as well as mixtures thereof.

The objective of the present invention is to provide an adjustment device for a housing, specifically a balance housing, which overcomes the drawbacks of the prior art. Accordingly, the adjustment device should be of a configuration which can be realized within a limited height, which is easy to operate, and which is protected against inadvertent changes of the adjustment setting.

SUMMARY

This task is solved by an adjustment device for a housing to adapt the latter to an uneven standing surface, wherein the adjustment device includes a foot piece with an internal thread forming a displacement axis. The foot piece is arranged in a recess of the housing which is accessible from the surface of the housing that faces towards the standing surface. Furthermore, the foot piece has a cross-sectional profile perpendicular to the displacement axis which in cooperation with the recess prevents a rotation of the foot piece about the displacement axis. The adjustment device further includes a spindle with an external thread that cooperates with the internal thread of the foot piece, and a levelling wheel connected to the spindle. The levelling wheel and the spindle are joined through a rotation-blocking connection.

As a result of the foot piece being arranged in a recess of the housing, a low height of the housing is achieved.

In a preferred embodiment, a stop is formed on the spindle between the external thread (8) and the spindle end that connects to the levelling wheel, while a counter-stop is formed on the housing, so that the counter-stop can be interposed or held captive between the stop and the levelling wheel. As a result of this arrangement, the spindle and the levelling wheel stay in place, i.e. they cannot move in the direction of the displacement axis, which is another favorable factor for a design of limited height.

According to a further concept of the invention which is followed in the design of the adjustment device, the degree of freedom of the spindle is limited to a rotation about the displacement axis. In other words, the spindle cannot perform a translatory movement along the displacement axis. This allows a compact design, since the adjustment device in the fully retracted position occupies no more space inside the housing than in the fully extended position. Or in other words, the adjustment device occupies a constant volume in the housing even at the ends of the adjustment range.

In a further developed embodiment of the invention, the housing is supported by the counter-stop resting on the stop of the spindle.

According to an advantageous further development of the invention, the housing rests on the supporting surface through at least three spindles.

In a further development of the invention, the rotation of the foot piece about the displacement axis is prevented by means of a form fit between the foot piece and the recess.

In an embodiment of the invention, the levelling wheel is releasably connected to the spindle by means of a snap connection. With the releasable snap connection, the adjustment device can easily be installed in, or removed from, the housing.

In a special further development of this embodiment, the snap connection works in the sense of a form-fitting connection.

In another special development of the foregoing embodiment, the snap connection works in the sense of a bayonet connection.

In a preferred embodiment, the foot piece can be accommodated entirely in the recess of the housing. In other words, the foot piece can in essence be completely integrated in the recess of the housing.

According to a further embodiment of the invention, turning the levelling wheel about the displacement axis causes the foot piece to move along the displacement axis either out of the recess or back into the recess.

According to a further concept of the invention which is followed in an embodiment of the adjustment device, the housing has a top which completely covers the levelling wheel.

In a special further development of an embodiment of the invention, the levelling wheel and the spindle are rotationally locked together with a flat portion on the circumference of a connector peg between the levelling wheel and the spindle.

In a preferred embodiment, a sole of a material different from the foot piece is attached to the surface of the foot piece that faces towards the support surface.

According to a further development of the invention, at least one stop element is attached to the surface of the foot piece that faces towards the stop on the spindle.

DETAILED DESCRIPTION

The housing2which is shown in a perspective view inFIG. 1has four mounting places for an adjustment device1located, respectively, at the four corners. Only the corner closest to the viewer has an adjustment device1installed. The foot piece3, which has a sole15as a contact layer against a supporting surface, can be seen protruding from the bottom of the housing2. The sole15can be made for example of a synthetic elastomeric material with the purpose of, e.g., improving adhesion to the supporting surface or attenuating ground vibrations. A levelling wheel9can be seen at the top end. The position of the protruding foot piece3is adjustable by turning the levelling wheel9.

The three-dimensional cutaway representation inFIG. 2allows an open view of the entire adjustment device. The foot piece3is arranged in a recess6of the housing2, wherein the cross-sectional profile of the recess6matches the cross-section of the foot piece3. The form fit between the recess and the foot piece prevents a rotation R of the foot piece3about the displacement axis4while allowing only a translatory displacement T along the displacement axis4.

The spindle7, which is not visible inFIG. 1, can be seen in the cutaway area ofFIG. 2. At one end, the spindle7carries an external thread8which cooperates with the internal thread of the foot piece3, while the other end of the spindle7is connected to the levelling wheel9. An intermediate section of the spindle7has a larger diameter than the threaded section8. The shoulder of the intermediate section10that faces towards the levelling wheel9serves as a stop10against the counter-stop11of the housing2.

Due to the connection of the levelling wheel9with the spindle7and the counter-stop11interposed between them, the spindle is prevented from a translatory movement T along the displacement axis4, except for a necessary amount of mechanical play. This means that a translatory movement T along the displacement axis4is not possible for the spindle7. The freedom of movement of the spindle7as well as of the levelling wheel9is limited to a rotation R about the displacement axis4. This allows a design with a limited height, since the adjustment device1in the fully retracted position occupies no more space inside the housing2than in the fully extended position. Or in other words, the adjustment device1takes up a constant volume in the housing2even at the ends of the adjustment range.

FIG. 2illustrates the connection between the spindle7and the levelling wheel9as a snap connection12in the sense of a releasable form-fitting connection. This connection is more clearly evident inFIG. 3and will therefore be described in a later context.

As the levelling wheel9is turned about the displacement axis4, the spindle7participates in the rotation due to the form-fitting connection and causes a translatory displacement T of the foot piece3along the displacement axis4. Thus, the housing2can be levelled horizontally on an uneven supporting surface by turning the appropriate levelling wheels9of the adjustment devices that are arranged at the corners.

As is commonly known, a full turn of the levelling wheel9causes a height change equal to the pitch of the screw thread. As the screw pitch is a design choice, the adjustment precision is selectable, with a smaller screw pitch allowing a finer adjustment.

FIG. 3shows the same adjustment device1in an exploded view, wherein the spindle7as well as the recess6can be seen more clearly. Also shown in this drawing are four stop contact elements16which are arranged on the end surface of the foot piece3that faces towards the spindle7. The purpose of the stop contact elements16is, among other factors, to prevent the foot piece3from seizing up. The stop contact elements16can be of the same material as the foot piece3and can be solidly attached, or they can be part of the same body as the foot piece3. It would also be conceivable to use stop contact elements16of a synthetic elastomer, so that they could also perform a damping function.

Clearly recognizable is the shape of the recess6which matches the outside contour of the foot piece3. It should be noted here that the outside contour could be of any conceivable shape, as long as the recess6can be formed in a corresponding shape and as long as it meets the condition that it prevents the foot piece3from turning about the displacement axis4.

As already mentioned above, the connection between the spindle7and the levelling wheel is shown in the drawing as a snap connection12in the sense of a releasable form-fitting connection. The spindle in the illustrated embodiment has a conically shaped circumference with a small protuberance which provides a form-fitting connection to the levelling wheel. In the assembly process of the adjustment device1the spindle7is inserted into the recess6, and the levelling wheel is pushed from the opposite side of the counter-stop11onto the conical peg of the spindle7. The levelling wheel9has a small groove—matching the size of the protuberance—inside the spindle seat, where the spindle can7can snap into engagement.

There are also other conceivable ways in which a releasable snap connection could be realized, and the same can be said for a bayonet connection. A bayonet connection is a coupling which allows a quick connection as well as release between two cylindrical parts in the direction of their longitudinal axis. The parts are joined together by plugging one into the other and twisting them relative to each other, using the reverse sequence to separate them from each other. In conventional bayonet connections between two elements, one element usually has a bayonet pin which is entered into an appropriately shaped slot or groove of the other element in the manner of a sliding guide mechanism and moved until the bayonet pin has reached an end position corresponding to the connected state of the two elements.

A flattened area17on the connector peg of the spindle7ensures that the spindle7and the levelling wheel9cannot turn relative to each other. In other words, they are joined by a rotation-blocking connection.

FIG. 4again represents the same housing2with two adjustment devices1in a three-dimensional view. In addition, a top14is shown which covers the housing2from above. In this assembled state, the levelling wheel9is neither visible nor operable. In this straightforward manner, the adjustment device1is not only protected against inadvertent changes of the adjustment settings, but also quickly made accessible again by simply removing the top14from the housing2.

FIG. 4further illustrates the important advantage that the adjustment device1allows the housing to have an extremely low profile which is only slightly taller than the height of the adjustment device1itself in its fully retracted state.

Although the invention has been described by presenting an example of a specific embodiment, it is considered evident that numerous further variants could be created based on the teachings of the present invention, for example by combining features of the individual embodiments with each other and/or by interchanging individual functional units between the embodiments.