Patent Description:
Many household appliances use a motor, pump, grinder or other actuator to provide (part of) the main functionality of the appliance. To prevent excessive vibration at the device housing and/or excessive mechanical vibration noise, suspension systems are used to reduce mechanical vibrations from the actuator unit to the device housing. Suspension systems are also often used to reduce vibration related noise and/or to control the sound characteristics (e.g. change noise perception).

Examples of standard suspension systems include car suspension components (coil springs, leaf springs, torsion bar springs etc.), mounting systems for air conditioning units on buildings, refrigerator and freezer pump mountings, washing machine drum mountings, mounting systems for vibration- or shock-sensitive devices such as stereo systems, compact disc players, as for example disclosed in <CIT>, and mountings for motors in kitchen appliances. These use various combinations of springs and rubber mountings.

In most cases, placing a vibrating component on a rubber suspension component or using a simple coil spring suffices. However, for several applications this approach does not provide enough mechanical decoupling and/or sufficient stabilization or alignment of the component. Examples include the coffee grinder of a fully automatic coffee machine, the pump of a coffee machine, and the pump of a steam iron, in which a combination of springs and rubber motor suspension parts and mounts are used.

Document <CIT> discloses a coffee machine according to the preamble of claim <NUM>.

Some basic vibration damping mounting systems will first be outlined, before the system of the invention is explained.

<FIG> shows an object <NUM> mounted on top of a spring <NUM> which is mounted to an underlying support <NUM>, and <FIG> shows an object <NUM> suspended from a spring <NUM> which hangs from a support <NUM> above.

<FIG> are representations in the 2D plane. To maintain the suspension function, the center of mass of the object is exactly in line with the mounting points of two ends of the spring. Otherwise, in <FIG> the object will topple over sideways and rotate around the top spring mounting point and in <FIG> the object will rotate around the bottom spring mounting until the center of mass is in line again with the spring mounting points. These rotary motions change the orientation of the object giving possible misalignment issues.

For the example <FIG>, toppling over can be prevented by the arrangement of <FIG> in which a second vertical spring <NUM> and a third horizontal spring <NUM> have been added. The second spring <NUM> restricts rotation of object and the third spring <NUM> restricts sideways movement of object.

For the example of <FIG>, rotation around the object-spring mounting point can be restricted by the arrangement of <FIG>, in which a second vertical pendulum spring <NUM> is added. When the object tries to rotate around its center of mass, it is now restricted, because the two springs <NUM>, <NUM> are placed at a horizontal distance from the center of mass of the object.

The free hanging arrangement of <FIG> and <FIG> function as a pendulum system. If the object is pushed sideways and then let go, the object will automatically swing back to its neutral bottom position, giving a stable and self-aligning arrangement.

It is evident therefore that alignment is more complicated and requires more springs with an object placed on top of a spring arrangement compared to an object hanging from a spring arrangement. In general, the more springs, the higher the residual vibration forces towards the device housing. A suspension design, where an object is hanging, is therefore preferred since it requires a smaller amount of springs.

One of the main issues with suspension systems is to maintain suspension performance while also taking care of all the six degrees of freedom of movement (<NUM>-DoF) of the object that is suspended. <NUM>-DoF includes the three translational movements and three rotational movements (around the center of mass) of the object. If any of the <NUM>-DoF is neglected, the object is considered unstable, often causing positioning issues, instability and/or additional vibration transmission (often via unintended other contact points).

The two pendulum spring solution of <FIG> is suitable for a design in a 2D plane. An additional pendulum suspension point needs to be added in order to provide a suspension point in the third dimension.

<FIG> shows a spring suspension system for an object <NUM> using three vertical springs <NUM> suspended below fixed rigid mounting points <NUM>. The object can be assumed to be a point mass. The object is aligned well, but any excitation of the object will result in a large horizontal movement and/or rotation around vertical and horizontal axes.

There is therefore a need for an improved suspension mounting.

According to examples in accordance with an aspect of the invention, there is provided a system comprising:.

This mounting design suspends an object, for which vibration damping is required, by a set of at least three springs (and preferably exactly three springs). The springs surround the object, and the bottom ends define a stable support plane. The object is supported by these bottom ends. In particular, the bottom ends of the set of springs define the only physical support for the object, i.e. it is fully suspended from above. The angle of vertical offset means the springs pull the object to the center, giving a form of pendulum effect. This gives the support stability and it aligns the object correctly in the horizontal plane. This avoids the need for additional supports, springs or damping systems and hence gives a reduced part count.

The object is thus hanging from a set of springs, such as a set of three angled springs, connected to a lower polygon which functions as a stabilization surface. The system makes use of the well-known pendulum effect to align the suspended object in the horizontal plane. The stabilization surface provides the stabilization of the object. This stabilization eliminates the need for additional supports thereby increasing the suspension performance with a reduced part count.

The angle of offset to the vertical is for example more than <NUM> degrees, for example more than <NUM> degrees. This applies during a normal operational orientation of the system. For example, for system intended to be mounted on a horizontal surface such as a kitchen worktop, the angles apply when the system is mounted on a horizontal surface,.

The angle of offset to the vertical is however preferably less than <NUM> degrees, for example less than <NUM> degrees.

The greater the angle, the greater the spring force that is needed to support the object vertically, but the greater the stabilizing forces.

The center of gravity of the object is preferably below a plane of the upper polygon. Thus, the object is suspended below the top polygon.

An upward vertical height from the plane of the lower polygon to the center of gravity is preferably less than a minimum distance between the center of gravity, when projected vertically onto the lower polygon, and the edges of the lower polygon. This gives the mounting stability against tipping over an edge of the lower polygon.

In one example, the center of gravity of the object is above the plane of the lower polygon. In this case, the upward vertical height is positive and should be less than the minimum distance as explained above.

In another example, the center of gravity of the object is below the plane of the lower polygon. In this case, the upward vertical height is less than zero, so this automatically meets the requirement to be less than the minimum distance as explained above.

The upper and lower polygons are preferably regular polygons.

The system may comprise exactly three springs. The upper and lower polygons are then triangles, preferably equilateral triangles.

The bottom end of each spring may comprise a support loop and the object comprises a set of feet which engage with the support loops. This makes the system easy to assemble. The object can simply be placed on the bottom ends of the springs (e.g. wire springs) using a notch or cone in feet of the object.

The top end of each spring may comprise a hook and the housing comprises receiving areas for receiving the hooks. This again makes easy assembly. The springs do not have to be bolted or clamped or rotationally hooked to the housing but can instead be slid linearly into place.

The system comprises a coffee machine. The object comprises an actuator which vibrates in use such as a motor or a component which incorporates a motor. A component which incorporates a motor is for example a coffee grinder, a fan or a pump.

The invention provides a system in which an object is mounted within a housing by a mounting which is to provide vibration damping for the object. The mounting comprises a set of at least three springs, each having a top end coupled to the housing and a suspended bottom end at which the object is supported. The top ends define an upper polygon and the bottom ends define a lower polygon. A center of gravity of the object is along a vertical line which passes through the lower polygon, and springs are angled inwardly towards the lower polygon.

As discussed above with reference to <FIG>, three vertical suspension springs may be used to provide good alignment of an object, but any excitation of the object will result in a large horizontal movement and/or rotation around vertical and horizontal axes.

<FIG> shows a first approach for improving the stability. Instead of suspending the object from vertical springs, the springs are angled so that they apply an outward pulling force as well as supporting the vertical weight of the object. The combination of these outward forces resists movement of the object away from its intended position within a horizontal plane. Thus, this improves the positional stability.

However, the rotational stability of the object remains an issue.

The invention is based on locating the attachment points to the object further away from its center of mass, creating a stability surface, in combination with the angled spring approach of <FIG>.

<FIG> shows an arrangement in accordance with the invention. It shows part of a system comprising a housing and an object <NUM> mounted within the housing.

The housing is schematically represented as three support pillars <NUM> and a base <NUM>. The tops of the pillars are the top mounting points <NUM> for a set of three springs <NUM>. Each spring <NUM> has a top end coupled to the housing at a mounting point <NUM> and a suspended bottom end.

The top ends, i.e. the three mounting points <NUM>, define the apices of an upper polygon, in this example a triangle, preferably an equilateral triangle. The bottom ends of the springs also define the apices of a lower polygon, in this example also a triangle, and preferably an equilateral triangle.

The lower polygon defines a stability surface <NUM>. However, this may be a virtual surface in the sense that there is no need for an actual planar support. Instead, the polygon and a virtual surface is defined by the three mounting points at the bottom ends of the springs <NUM>. When the center of mass of the object is placed within this stability surface (or projects vertically onto this stability surface), the object will not rotate around the horizontal axes and is thus kept stable. The larger the (minimum) radius R from center of mass to the edges of the lower polygon (limiting the stability surface), the more stable the object becomes.

The radius R is the smallest perpendicular distance from the location of the center of gravity projected onto the plane of the stability surface and an edge of the lower polygon.

In general, a rotational moment M around the center of mass is divided by the arm length, i.e. radius R, resulting in a low force trying to rotate the object (if R is large) by trying to elongate the springs.

The angled springs used in <FIG> (and also shown in <FIG>) thus stabilize the object with respect to rotation around the vertical axis as well as stabilizing the object position with respect to translation in the horizontal axes. In particular, the position stabilization is controlled by the spring stiffness rather than friction at the hinge points. The spacing R further stabilizes the object with respect to rotation around the horizontal axes.

The more angled the springs are oriented to the vertical, the larger the stability. However, this increased stability is at the cost of an additionally required tension in the spring to keep the object at the correct height, since only a portion of the spring tension is acting to support the weight of the object.

<FIG> shows the force directions for the vertical pillar force Fpillar (the upward force the pillar needs to provide to carry the object). For each pillar, this is one third of the object weight. A stabilization force Fstab acts horizontally. Thus, the spring force Fspring needs to increase to maintain the same vertical force Fpillar if the angle α is increased in order to increase the stabilizing force Fstab.

The angled springs result in a taper inwardly between the upper polygon and the lower polygon, i.e. the upper polygon is a larger triangle than the lower polygon in this example. The angled springs pull the object to the center, giving a form of pendulum effect. This gives the support stability and it aligns the object correctly in the horizontal plane. This avoids the need for additional supports, springs or damping systems and hence gives a reduced part count.

The angle α of offset to the vertical of the springs is for example more than <NUM> degrees, for example more than <NUM> degrees. It is for example less than <NUM> degrees, for example less than <NUM> degrees.

The arrangement of <FIG> gives improved mechanical decoupling compared to a standard object mounted on a spring or a rubber mounting solution. The design reduces the number of parts needed by avoiding the need for additional features to prevent misalignment or toppling of the suspended object.

The basic approach is to suspend the object using a least number of spring elements as possible, and space the suspension points far apart from each other in order to create a large stability surface, e.g. triangle.

For the arrangement of <FIG>, in the vertical direction, the center of mass of the object should be below the top mounting points <NUM> of the springs <NUM> so that the object is indeed suspended. In addition, the vertical distance H of the center of mass of the object to the plane of the lower polygon (in this case a stability triangle) should be less than R as defined above. This makes sure the object on the stability surface does not topple over on its stability plane along one of the edges of the lower polygon.

Note that the center of mass of the object may be below the plane of the lower polygon, in which case H is negative, so that H < R is satisfied no matter how far the center of mass lies below the plane of the lower polygon.

The invention has been tested for mounting a grinder motor of an integrated bean grinder of a coffee machine.

<FIG> shows the bean grinder viewed from beneath. It comprises a motor <NUM> which drives a grinding wheel <NUM> within a housing <NUM>. The housing has three support feet <NUM> which define the lower polygon <NUM>. The mounting for example aims to achieve approximately 10dB of noise reduction.

One of the springs is shown in <FIG>. It comprises a wire (in a closed shape) having a hook portion <NUM> at the top and a support loop <NUM> at the bottom. The support feet of the grinder each sit on a respective support loop. Each support foot for example comprises a projection, e.g. a conical projection, which fits through the support loop <NUM>.

The spring is thus a wire loop rather than a coil spring. The spring force is primarily from the bend at the top of the hook portion. The hook portion <NUM> for example pushes (linearly) into a slot of the housing of the coffee machine and the bean grinder then simply rests on the support loops <NUM>. The inward extension of the support loop defines the effective angle of the spring. Thus the angle is defined between the effective contact point between the support loop and the object foot and the effective contact point between the hook portion <NUM> and the housing.

The use of a wire spring is beneficial when there is limited space around the object to be suspended (especially when taking into account the required clearances for function and drop tests). A wire spring is also able to avoid resonance frequencies of the spring at the operating frequency range of the object (e.g. grinder) to ensure sufficient vibration isolation for noise reduction.

The system is also easy to assemble with a simple stacking operation. The springs do not need to be bolted, clamped or rotationally hooked at the housing. Instead, they can be slid into place. The spring design is such that the object is placed on low support loops with a simple interface such as a notch or cone to make sure the springs and object stay connected.

When there are three springs, they are arranged in a triangle, so the housing of the coffee machine has three slots for receiving the three springs, around the area where the bean grinder will be located.

The example above is based on the use of three springs, and this represents the minimum number of components. However, more than three springs may be used, for example with square upper and lower polygons for four springs, pentagonal upper and lower polygons for five springs, etc. Up to ten springs may conceivably be used, but it is preferred to use as few components as possible to achieve the desired damping performance.

The invention is of particular interest for household appliances, such as drinks machines, for example coffee machines. It may be used for suspending any motor, or component having a motor, such as a pump or grinder.

Indeed, the invention is applicable generally to any coffee machine with a fan, pump, or motor, which is mounted with a particular orientation.

Claim 1:
A coffee machine comprising:
a housing (<NUM>,<NUM>); and
an object (<NUM>) comprising an actuator which vibrates in use, mounted within the housing by a mounting which is to provide vibration damping for the object, wherein:
the mounting comprises a set of at least three springs (<NUM>), each having a top end coupled to the housing and a suspended bottom end;
the top ends define the apices of an upper polygon;
the bottom ends define the apices of a lower polygon (<NUM>);
the object (<NUM>) is supported by the bottom ends of the set of springs; and
in an intended operational orientation of the system, the center of gravity of the object is along a vertical line which passes through the lower polygon, characterized in that the line between the top end and bottom end of each spring is offset from the vertical, such that the lines taper inwardly between the upper polygon and the lower polygon.