GB2463900A

GB2463900A - Coffee dispensing apparatus having a grinding mechanism

Info

Publication number: GB2463900A
Application number: GB0817752A
Authority: GB
Inventors: Alexander Stuart Knox; Charles Edward Park
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2008-09-27
Filing date: 2008-09-27
Publication date: 2010-03-31
Also published as: GB0817752D0

Abstract

A beverage ingredient dispenser 24 comprising a hopper 66 for storing a beverage ingredient e.g. coffee beans; a grinder 76 for receiving the beverage ingredient from the hopper 66 via a first auger 84 comprising a first grinding element 78, and a second grinding element 80 located on a shaft 82 which is rotatable about an axis X-X to rotate the second grinding element 80 relative to the first grinding element 78, each grinding element comprising a respective grinding surface. The dispenser 24 also has an adjustable stop member (104, Fig.6) moveable along the axis X-X for limiting axial movement of the grinding surface of the second grinding element 80 away from the grinding surface of the first grinding element 78 during a grinding process. The adjustable stop member (104, Fig.6) may be a collar that extends around the axis X-X.

Description

Domestic Appliance The present invention relates to apparatus for dispensing a beverage ingredient, and to a domestic appliance including such apparatus.

Domestic coffee grinders for grinding coffee beans and dispensing ground coffee for use in brewing a beverage are well known. For example, US 5,172,868 describes a coffee grinding apparatus comprising a drive shaft and a motor for rotating the drive shaft. A grinder comprises a stationary grinding element, and a rotary grinding element located on the drive shaft for rotation relative to the stationary grinding element. An auger is located on the shaft for conveying coffee beans to the grinder. The ground coffee produced by the grinder falls into a suitable receptacle for collection.

It is also known to incorporate a coffee grinder within a coffee machine so that a beverage may be prepared using freshly-ground coffee. For example, EP 0 804 894 describes a coffee machine comprising a hopper for storing coffee beans, a grinder, an auger located within the hopper for conveying coffee beans from the hopper to the grinder, and a brewing assembly arranged to receive ground coffee from the grinder.

The coarseness of the ground coffee produced by the grinder determines the rate of extraction of coffee oils and compounds from the ground coffee during the brewing process, thereby determining the flavour of the coffee beverage produced by the machine. As the grinding surfaces of the grinder wear away over time, the distance between the grinding surfaces will gradually increase, and this in turn will increase the coarseness of the ground coffee produced by the grinder. In view of this, it is known to provide a mechanism for allowing the spacing between the grinding surfaces of the grinder to be adjusted. One such mechanism comprises an adjustment ring nut threaded to the housing of the grinder, arid which is rigidly attached to the stationary grinding element. By manually turning the adjustment ring nut, the distance between the grinding surfaces of the grinding elements can be adjusted.

To facilitate the turning of the adjustment ring nut, part of its outer periphery may be exposed by the housing of the grinder. In this case, there is a risk that the adjustment ring nut may be accidentally rotated, either during use or between uses, thereby causing the spacing between the grinding surfaces to be inadvertently changed. To avoid this, the adjustment ring nut may be located entirely within the housing of the grinder. In this case, either the user may be required to remove part of the housing in order to access the adjustment ring nut, which can be inconvenient for the user, or an automated system may be provided for rotating the adjustment ring nut, which can add significant cost to the grinder.

It is an aim of at least the preferred embodiment of the invention to provide an alternative mechanism for allowing the spacing between the grinding surfaces of a grinder to be adjusted.

The present invention provides apparatus for dispensing a beverage ingredient, comprising a hopper for storing a beverage ingredient, a grinder for receiving a beverage ingredient from the hopper and for producing ground beverage ingredient therefrom, the grinder comprises a first grinding element, and a second grinding element located on a shaft which is rotatable about an axis to move the second grinding element relative to the first grinding element, each grinding element comprising a respective grinding surface, and an adjustable stop member moveable along the axis for limiting axial movement of the grinding surface of the second grinding element away from the grinding surface of the first grinding element during a grinding process.

During grinding, the force exerted on the grinding surfaces by the beverage ingredient located therebetween will tend to urge the grinding elements apart, and therefore move the second grinding element and the shaft along the axis. By providing an adjustable stop member which is moveable along this axis, an upper limit to the distance which the second grinding element can move away from the first grinding element during a grinding process, and thus an upper limit to the separation between the grinding surfaces of the grinding elements, can be easily and rapidly changed.

In a preferred embodiment the stop member extends about the axis to provide an annular abutment surface for limiting the axial movement of the second grinding element. The stop member may be located anywhere along the shaft, but in a preferred embodiment the stop member is located at or towards one end of the shaft. The apparatus preferably comprises an auger for conveying beverage ingredient to the grinder, and which is preferably located between the grinder and the stop member.

In a preferred embodiment the stop member is threadedly connected to a housing for the grinder so that the stop member can be readily moved along the axis by rotation thereabout. The stop member may be rotated directly by the user, but in a preferred embodiment a manually-operable adjustment member is provided for moving the stop member relative to the housing. The adjustment member may comprise a rotatable sleeve extending about the axis and which is connected to the stop member. In order to prevent accidental movement of the stop member, the adjustment member is preferably moveable relative to the stop member between a stowed position in which rotation of the stop member is inhibited and a deployed position in which the stop member is rotatable relative to the housing. The adjustment member is preferably biased towards the stowed position so that the adjustment member returns automatically to the stowed position once it has been released following adjustment of the position of the stop member. The adjustment member and the housing may each be provided or formed with a plurality of teeth which mesh together when the adjustment member is in the stowed position.

In a preferred embodiment, the apparatus comprises a drive mechanism for driving rotation of the shaft, with the shaft being axially moveable relative to the drive mechanism to disengage the shaft from the drive mechanism. The stop member may be conveniently arranged to abut a driven member located on the shaft for connecting the shaft to the drive mechanism. The stop member may extend about the driven member, and may comprise a shoulder extending radially inwardly towards the shaft, with the driven member comprising a radially extending abutment surface facing the shoulder of the stop member.

The present invention extends to domestic appliance comprising apparatus as aforementioned. The apparatus is preferably moveable relative to a casing of the appliance to allow a user to move the stop member relative to the shaft.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a coffee machine; Figure 2 is a perspective view of the coffee machine of Figure 1 showing an access door in an open position; Figure 3 is a schematic illustration of components of the coffee machine of Figure 1; Figure 4 is a side view of the ingredient drawer of the coffee machine of Figure 1; Figure 5 is a cross-sectional view of the ingredient drawer of Figure 4; Figure 6 is a close-up of part of Figure 5; Figure 7 is a cross-sectional view of the ingredient drawer of Figure 4 connected to a drive assembly; Figure 8 is side view of the ingredient drawer of Figure 4, with a grinder adjustment assembly in a deployed position; and Figure 9 is a cross-sectional view of the ingredient drawer as illustrated in Figure 8.

Figure 1 illustrates a domestic appliance. In this embodiment the domestic appliance is in the form of a coffee machine 10 that is suitable for domestic use in, for example, a kitchen environment. The coffee machine 10 has a substantially cuboid outer casing 12.

The outer casing has an upper surface 14 and a front surface 16. A spout 18 is located in the front surface 16 of the outer casing 12. The spout 18 is moveable relative to the casing 12 between a deployed position, illustrated in Figure 1, in which the spout 18 extends from the casing 12 to dispense coffee from the coffee machine 10, and a stowed position, illustrated in Figure 2, in which the spout 18 is stored within the casing 12. A more detailed description of the spout 18 can be found in co-pending application An access door 20 is formed in the outer casing 12. The access door 20 forms a part of the front surface 16 of the casing 12 and is slidably openable between a closed position, illustrated in Figure 1, in which the access door 20 is flush with the front surface 16 of the casing 12, and an open position, illustrated in Figure 2. The access door 20 is attached to an ingredient drawer 22 which moves therewith. For example, the ingredient drawer 22 may be arranged to slide along runners attached to, or integral with, the inner surfaces of the casing 12. The ingredient drawer 22 comprises a storage assembly 24 for storing a beverage ingredient (for example, coffee beans or pre-ground coffee) for use in preparing a coffee beverage.

The coffee machine 10 has a user-operable control panel 26 located on the upper surface 14. The control panel 26 may comprise a touch-sensitive screen and/or a plurality of buttons to enable the user to control the operation of the coffee machine 10.

A water reservoir 28 is located adjacent to the outer casing 12 and is attached thereto by a base portion 30. The water reservoir 28 has a substantially cuboid body 32 which may be formed from a transparent material such as a plastics material, or from an opaque plastics material. In this latter alternative the body 32 may be provided with a window to enable the user to see the volume of water within the water reservoir 28. An aperture 34 is formed in the upper end of the body 32 to enable the user to introduce water to the water reservoir 28. The aperture 34 is closed by a hinged lid 36 which is openable by a user. The lid 36 is shown in the closed position in Figures 1 and 2. The operation of the lid 36 is described in more detail in co-pending application GB 0723823.1 and will not be discussed any further here.

A valve unit 38 connects the water reservoir 28 to the base portion 30. The valve unit 38 has a first portion located in the body 32 and a second portion located on the base portion 30. The water reservoir 28 is removable from the base portion 30 to enable the water reservoir 28 to be placed under a domestic water tap for filling. The water reservoir 28 can be released from the base portion 30 by pulling the water reservoir 28 upwardly away from the base portion 30. When this occurs, the first and second portions of the valve unit 38 are separated. This action automatically closes the valve unit 38, preventing leakage of water from the water reservoir 28.

Figure 3 illustrates schematically the components of the coffee machine 10. A reservoir conduit 40 located in the base porti9n 30 connects the water reservoir 28 (via the valve unit 38) to a pump 42. The pump 42 is located within the outer casing 12 of the coffee machine 10. In this embodiment, the pump 42 is a solenoid pump. Downstream of the pump 42 is an inline heater element 44 for heating water drawn from the water reservoir 28 by the pump 42. The heater element 44 is arranged to heat the water passing therethrough to a temperature of around boiling point. A supply conduit 46 is located downstream of the heater element 44 and is arranged to supply water to a brewing assembly 50. The brewing assembly 50 is also arranged to receive ground coffee from an ingredient dispenser 52 arranged to receive coffee beans or ground coffee from the storage assembly 24. A dispensing conduit 54 connects the brewing assembly 50 to the spout 18 tb allow a prepared coffee beverage to be dispensed. A waste grounds container 56 is provided beneath the brewing assembly 50 to receive waste ground coffee from the brewing assembly 50 following the completion of a beverage preparation by the coffee machine 10.

A controller 58 is provided for controlling the operation of the coffee machine 10. As described in more detail below, the controller 58 is arranged to receive signals from the control panel 26 and from the ingredient dispenser 52, and to operate the pump 42, heater element 44, brewing assembly SO and the ingredient dispenser 52 in response thereto.

The ingredient drawer 22 is illustrated in more detail with reference to Figures 4 to 6.

The ingredient drawer 22 comprises a housing 60 having an upper portion 62 and a lower portion 64 connected to the upper portion 62. The upper portion 62 of the housing 60 defines the storage assembly 24, which comprises a first hopper 66 for receiving and storing a first beverage ingredient, in this example coffee beans, and a second hopper 68 for receiving and storing a second beverage ingredient, in this example ground coffee. The first hopper 66 has an open upper end through which coffee beans are introduced thereto, and which is closed by a removable lid 70.

Similarly, the second hopper 68 has an open upper end through which ground coffee is introduced thereto, and which is closed by a flap 72 pivotably mounted on the upper portion 62 of the housing 60.

The upper portion 62 and the lower portion 64 of the housing 60 together house the ingredient dispenser 52. The ingredient dispenser 52 is arranged to receive beverage ingredients from the hoppers 62, 64, and to dispense a selected ingredient from ingredient outlet 74 to the brewing assembly 50. The ingredient dispenser 52 comprises a grinder 76 for receiving coffee beans from the first hopper 64. The grinder 76 comprises an outer grinding element 78 connected to the housing 60, and an inner grinding element 80 which is rotatable within and relative to the outer grinding element 78. The inner grinding element 80 is located on a shaft 82 having an axis of rotation X-X. The grinding elements 78, 80 each comprise a respective grinding surface or burr which effect a grinding action when the inner grinding element 80 is rotatably driven in a first direction Dl about axis X-X, but which do not effect a grinding action when the inner grinding element 80 is rotatably driven in a second direction D2, opposite to direction Dl, about axis X-X.

The ingredient dispenser 52 also comprises a first auger 84 and a second auger 86. The first auger 84 is located towards the base of the first hopper 66, and is located on the shaft 82 for rotation about the axis X-X. The first auger 84 is arranged to feed coffee beans from the first hopper 66 to the grinder 76 when the shaft 82 is driven in the first direction Dl, and to move coffee beans away from the grinder 76 when the shaft 82 is driven in the second direction D2. The second auger 86 is located towards the base of the second hopper 84 and is also located on the shaft 82 for rotation about the axis X-X.

The second auger 86 is arranged to feed ground coffee from the second hopper 68 to the ingredient outlet 74 when the shaft 82 is driven in the second direction D2, and to move ground coffee away from the ingredient outlet 74 when the shaft 82 is rotated in the first direction DI. The ingredient outlet 74 may comprise a wall 87 located between the grinder 76 and the second auger 86 to prevent ground coffee produced by the grinder 76 from mixing with pre-ground coffee located within the second hopper 68.

With reference to Figure 7, the coffee machine 10 comprises a motorised drive mechanism 88 for driving the shaft 82 to rotate in a selected one of the first direction Dl and the second direction D2. The ingredient dispenser 52 is arranged to be connected to the drive mechanism 88 when the ingredient drawer 22 is in the stowed position, and to be disconnected from the drive mechanism 88 when the ingredient drawer 22 is in the deployed position. Returning to Figures 5 and 6, the ingredient dispenser 52 comprises a driven member for connecting the shaft 82 to the drive mechanism 88. In this example, the driven member comprises a driven dog 90 fastened to the end of the shaft 82 which is remote from the access door 20 by a screw 92. The driven dog 90 may be connected to the shaft 82 by an alternative mechanism, for example by shrink fitting.

The driven dog 90 is formed with a bore 94 for receiving a drive dog 96 (illustrated in Figure 7) of the drive mechanism 88. The drive dog 96 has a profiled outer surface arranged to engage a conformingly-profiled inner wall 98 of the driven dog 90 so that the driven dog 90 rotates with the drive dog 96. The housing 60 is shaped to define an aperture 100 through which the drive dog 96 passes towards the driven dog 90 as the ingredient drawer 22 is moved to the stowed position.

The coarseness of the ground coffee produced by the grinder 76 determines the rate of extraction of coffee oils and compounds from the ground coffee during the brewing process, thereby determining the flavour of the coffee beverage produced by the machine. The optimum coarseness of the ground coffee produced by the grinder 76 will vary depending on the type of coffee bean introduced to the first hopper 66; some coffee beans should be ground relatively coarsely for optimum flavour, whereas other coffee beans should be ground relatively finely. The coarseness of the ground coffee produced by the grinder 76 is dependent on the distance between the grinding surfaces of the grinding elements 78, 80 during grinding; when the distance between the grinding surfaces is relatively small the ground coffee will be relatively fine, whereas when the distance between the grinding surfaces is relatively large the ground coffee will be relatively coarse.

During grinding, the force exerted on the grinding surfaces of the grinding elements 78, will tend to urge the grinding surfaces apart. In this example, the grinding surfaces of the grinding elements 78, 80 are arranged so that the shaft 82 is urged to the left (as illustrated in Figures 4 to 6) during grinding. In view of this, the ingredient dispenser 52 comprises a grinder adjustment mechanism 102 for setting an upper limit for the spacing between the grinding surfaces of the grinding elements 78, 80 during grinding, thereby setting an upper limit for the coarseness of the ground coffee produced by the grinder 76. The grinder adjustment mechanism 102 comprises an adjustable stop member which is moveable along the axis X-X for limiting the movement of the driven dog 90, and thus the shaft 82, to the left during grinding. In this example the adjustable member comprises a collar 104 which surrounds the driven dog 90, and comprises an annular shoulder 106 providing a stationary abutment surface against which the driven dog 90 is urged during grinding. The driven dog 90 comprises an annular surface 107 which is located directly opposite to the shoulder 106 of the collar 104. The collar 104 is attached to the housing 60 by a screw thread arrangement comprising a helical thread 108 extending about one end of the collar 104 which is located within a conformingly-profiled helical groove 110 formed in the housing 60. Consequently, with rotation of the collar 104 relative to the housing about the axis X-X the shoulder 106 is moved along the axis X-X. A bearing 112 is located between the driven dog 90 and the collar 104 to inhibit rotation of the collar 104 with rotation of the driven dog 90.

The grinder adjustment mechanism 102 further comprises a manually-operable adjustment member for rotating the collar 104 relative to the housing 60. In this example the adjustment member comprises a sleeve 114 extending about the collar 104 for rotating the collar 104 relative to the housing 60. The sleeve 114 comprises a plurality of axially-extending grooves 116 formed in and angularly spaced about its inner surface. The collar 104 comprises a plurality of ribs 118 formed in and angularly spaced about its outer surface, and which are each located within a respective groove 116. This arrangement of grooves 116 and ribs 118 allows the sleeve 114 to slide along the axis X-X relative to the collar 104 and to rotate the collar 104 with rotation thereof.

The grinder adjustment mechanism 102 comprises means for inhibiting the rotation of the sleeve 114 during grinding. The sleeve 114 is biased towards the housing 60, and thus towards a stowed position by a resilient member in the form of a compression spring 120 located between the collar 104 and the sleeve 114. As illustrated in Figure 6, one end of the spring 120 engages an annular wall 122 of the sleeve 114, and the other end of the spring 120 engages second annular wall 124 of the collar 104 so as to urge the annular wall 122 of the sleeve 114 towards an annular end wall 126 of the housing 60. This end wall 126 of the housing 60 is formed with a plurality of teeth 128 which mesh with a plurality of teeth 130 extending about the sleeve 114 to inhibit rotation of the sleeve 114 relative to the housing 60.

A user may wish to adjust the upper limit for the spacing between the grinding surfaces of the grinding elements 78, 80 during grinding for one of a number of reasons. For example the user may wish to change this limit when introducing different coffee beans into the first hopper 66, when requiring the coffee beverage to have a different flavour, or periodically to accommodate for wear of the grinding surfaces of the grinding elements 78, 80 over time. To adjust the position of the collar 104, and thereby adjust the upper limit for the spacing between the grinding surfaces of the grinding elements 78, 80 during grinding, the ingredient drawer 22 is withdrawn from the casing 12 by actuating movement of the access door 20 from its closed position. This movement may be actuated by pressing an appropriate button on the control panel 26, which causes a solenoid mechanism to be actuated to push the access door 20 away from the casing 12. The user may then manually pull the ingredient drawer 22 to a fully open position in which the driven dog 90 of the ingredient dispenser 52 is spaced from the drive dog 96 of the drive mechanism 88, and in which the grinder adjustment mechanism 102 is accessible by the user. The ingredient drawer 22 may remain located within the runners located on the inner surfaces of the casing 12 when in its fully open position, or it may be entirely removable from the casing 12 by the user to allow the grinder adjustment mechanism 102 to be operated easily by the user.

The user then pulls the sleeve 114 away from its stowed position against the force of the spring 120 to a deployed position in which that the teeth 130 of the adjustment sleeve 114 are no longer meshed with the teeth 128 of the housing 60, as illustrated in Figures 8 and 9. The grinder adjustment mechanism 102 is configured such that the ribs 116 of the collar 104 remain located within the grooves 114 of the sleeve 114 when the sleeve 114 is in a deployed position. With the sleeve 114 spaced from the housing 60, the user rotates the sleeve 114 to cause the collar 104 to rotate about the axis X-X. In view of the threaded attachment of the collar 104 to the housing 60, the rotation of the collar 104 causes the shoulder 106 of the collar 104 to move along the axis X-X.

When the shoulder 106 of the collar 104 moves to the right (as illustrated in Figure 6), this will cause the bearing 112 and drive dog 90, and thus the shaft 82, to be moved along the axis X-X with the shoulder 106. As a result, the grinding surface of the inner grinding element 80 will be moved towards the grinding surface of the outer grinding element 78, thereby reducing the spacing between the grinding surfaces of the grinding elements 78, 80. Consequently, during use the grinder 76 will produce a relatively fine ground coffee. On the other hand, when the shoulder 106 of the collar 104 moves to the left (as illustrated in Figure 6), this will cause the shoulder 106 to move away from the annular surface 107 of the drive dog 90, and so the shaft 82 remains stationary.

However, during a subsequent grinding operation the forces exerted on the grinding surfaces of the grinding elements 78, 80 urge the grinding surfaces apart, forcing the shaft 82 to move to the left and thus driving the drive dog 90 and bearing 112 against the shoulder 106. Consequently, during use the grinder 76 will produce a relatively coarse ground coffee. Markings may be formed on the outer surface of the sleeve 114 to advise the user of the appropriate direction in which the sleeve 114 is to be rotated for the production of coarser or finer ground coffee by the grinder 76.

Once the user has rotated the sleeve 114 by the required amount, the user releases the sleeve 114. Under the force of the spring 122, the sleeve 114 is returned to it stowed position, as illustrated in Figures 4 to 6, in which the teeth 130 of the sleeve 114 mesh with the teeth 128 of the housing 60 so that further rotation of the sleeve 114, and thus further rotation of the collar 104, is inhibited during the grinding process. The user then pushes the access door 20 back to its closed position, in which the drive dog 96 of the drive mechanism 88 engages the inner wall 98 of the driven dog 90 to connect the drive mechanism 88 to the shaft 82.

Returning now to Figure 7, the drive mechanism 88 comprises a motor 140 and a gear arrangement 142 driven by the motor 140. The motor 140 is arranged to rotate in first and second direction Dl, D2 about an axis which is perpendicular to the axis X-X. The direction and the speed of rotation of the motor 140 is controlled by the controller 58.

The gear arrangement 142 comprises a first bevel gear 144 connected to the motor 140 by a compound gear (not shown) and which meshes with a second bevel gear 146 connected to a drive shaft 148. The drive shaft 148 is co-axial with the shaft 82 of the ingredient dispenser 52. The gear arrangement 142 thus translates the rotational motion of the motor 140 through 90° so that the drive shaft 148 is driven to rotate in the first and second directions Dl, D2 by the motor 140.

A drive clutch 1 50 is connected to the second bevel gear 146 for rotation therewith.

The drive clutch 150 is arranged to drive the drive dog 96 of the drive mechanism 88.

The drive clutch 150 is axially slidable relative to the second bevel gear 146, and so a clutch spring 152 is located between the second bevel gear 146 and the drive clutch 150 for urging the drive clutch 150 towards the drive dog 96, and for damping the movement of the drive clutch 150 relative to the second bevel gear 146. A plurality of clutch balls 1 54 are located between the drive clutch 150 and the drive dog 96 for transmitting torque from the drive clutch 150 to the drive dog 96. The clutch balls 154 are located within circular apertures formed in a ball plate 156 located between the drive clutch 150 and the drive dog 96. The facing surfaces of the drive clutch 150 and the drive dog 96 are each formed with an annular race comprising a plurality of circumferentially spaced recesses for receiving the clutch balls 154, and within which the clutch balls 154 are normally located. An optical sensor 158 is mounted on the housing 160 of the drive mechanism 88 for monitoring the rotation of the drive dog 96.

The sensor 158 is arranged to output a signal to the controller 58 after each revolution, or partial revolution, of the drive dog 96.

To prepare a beverage, a user introduces coffee beans into the first hopper 66 andlor ground coffee into the second hopper 68. The user then selects a mode of operation using the control panel 26. If the user selects freshly ground coffee, then the controller 58 operates the motor 140 to rotate in the first direction Dl. The gear arrangement 142 transfers the rotation of the motor 140 to the drive clutch 150, which drives the drive dog 96 to rotate in the first direction Dl, and which in turn drives the driven dog 90 and the shaft 82 of the ingredient dispenser 52. The coffee beans in the first hopper 66 are moved towards the grinder 76 by the first auger 84, where they are ground between the grinding surfaces of the grinding elements 78, 80. The freshly-ground coffee passes through the grinder 76, and is dispensed from the ingredient outlet 74 to the brewing assembly 50 for use in preparing a coffee beverage.

During this operation, the second auger 86 will also rotate in the first direction Dl.

However, because the helical screw of the second auger 86 is arranged in an opposing direction to that of the first auger 84, the second auger 86 will push ground coffee in the second hopper 66 away from the ingredient outlet 74, and so no pre-ground coffee will be dispensed with the freshly ground coffee.

During the grinding of the coffee beans by the grinder 76, with a constant speed of rotation of the motor 140 the rotational speed of the inner grinding element 78 is likely to fluctuate. For example, when relatively hard beans are being ground, the rotational speed of the inner grinding element 78 will be relatively slow due to the increased amount of work required to grind the beans, whereas when relatively soft beans are being ground, the rotational speed of the inner grinding element 78 will be relatively fast. Other factors which influence the rotational speed of the inner grinding element 78 include the spacing between the grinding surfaces of the grinding elements 78, 80, and the size of the coffee beans. Consequently, the amount of freshly ground coffee supplied to the brewing assembly 50 is dependent on the number of revolutions of the inner grinding element 78, rather than on the duration of the grinding operation.

The number of revolutions of the inner grinding element 78 during the grinding operation will be the same as the number of revolutions of the drive dog 96. In view of this, the controller 58 monitors the signals output from the optical sensor 158, and terminates the grinding operation once the number of revolutions of the drive dog 96 has reached a pre-set amount so that the required amount of freshly ground coffee is supplied to the brewing assembly 50.

From the signals output from the optical sensor 158, the controller 58 may also determine the current angular speed of the drive dog 96, and thus the current rate at which freshly ground coffee is being supplied to the brewing assembly 50. Depending on the current angular speed of the drive dog 96, the controller 58 may vary the speed of the motor 140. For example if the angular speed of the drive dog 96 is relatively low, the controller 58 may increase the speed of the motor 140 in order to increase the amount of torque supplied to the grinder 76 and thus increase the grinding speed. This can reduce the amount of time required to supply the required amount of freshly ground coffee to the brewing assembly 50, and thus reduce the amount of time required to produce the beverage. Furthermore, a relatively constant grinding speed can be achieved, thereby allowing the size of the coffee grinds and the grinding temperature to be maintained at relatively constant levels during the grinding process.

In the event that the grinder 76 becomes jammed during a grinding operation, the drive dog 96 will stop rotating. This causes the clutch balls 154 to roll out from the circumferentially spaced recesses located in the facing surfaces of the drive dog 96 and the drive clutch 150 and push the drive clutch 150 away from the drive dog 96, thereby allowing the drive clutch 150 to rotate freely relative to the stationary drive dog 96 and preventing the motor 140 from becoming overloaded. From the signals output from the optical sensor 158, the controller 58 determines that the drive dog 96 has stopped rotating, and stops the rotation of the motor 140. The controller 58 may then generate an alert to advise the user that the grinder 76 has become jammed.

If, on the other hand, the user selects pre-ground coffee then the controller 58 operates the motor 140 to rotate in the second direction D2. The gear arrangement 142 transfers the rotation of the motor 140 to the drive clutch 150, which drives the drive dog 96 to rotate in the second direction D2, and which in turn drives the driven dog 90 and the shaft 82 of the ingredient dispenser 52 in that direction. The pre-ground coffee within the second hopper 68 is transported by the second auger 86 to the ingredient outlet 74.

During this operation the first auger 84 will also rotate in the second direction D2.

However, because the helical screw of the first auger 84 is arranged in an opposing direction to that of the second auger 86, the first auger 84 will push coffee beans away from the grinder 76. Additionally, the grinding surfaces of the grinding elements 78, 80 are arranged so that no grinding takes place when the inner grinding element 80 is rotated in the second direction D2, and so no freshly ground coffee is supplied to the ingredient outlet 74.

Claims

CLAIMS1. Apparatus for dispensing a beverage ingredient, comprising: a hopper for storing a beverage ingredient; a grinder for receiving a beverage ingredient from the hopper and for producing ground beverage ingredient therefrom, the grinder comprises a first grinding element, and a second grinding element located on a shaft which is rotatable about an axis to rotate the second grinding element relative to the first grinding element, each grinding element comprising a respective grinding surface; and an adjustable stop member moveable along the axis for limiting axial movement of the grinding surface of the second grinding element away from the grinding surface of the first grinding element during a grinding process.
2. Apparatus as claimed in claim 1, wherein the stop member extends about the axis.
3. Apparatus as claimed in claim I or claim 2, wherein the stop member is located at or towards one end of the shaft.
4. Apparatus as claimed in any one of the preceding claims, comprising an auger for conveying beverage ingredient to the grinder, and wherein the auger is located between the grinder and the stop member.
5. Apparatus as claimed in any one of the preceding claims, wherein the grinder is located in a housing, and wherein the stop member is threadedly connected to the housing.
6. Apparatus as claimed in claim 5, comprising a manually-operable adjustment member connected to the stop member for rotating the stop member relative to the housing.
7. Apparatus as claimed in claim 6, wherein the adjustment member comprises a sleeve extending about the stop member.
8. Apparatus as claimed in claim 6 or claim 7, wherein the adjustment member is moveable relative to the stop member between a stowed position in which rotation of the stop member is inhibited and a deployed position in which the stop member is rotatable relative to the housing.
9. Apparatus as claimed in claim 8, wherein the adjustment member is biased towards the stowed position.
10. Apparatus as claimed in claim 8 or claim 9, wherein the adjustment member and the housing each comprise a plurality of teeth which mesh together when the adjustment member is in the stowed position.
11. Apparatus as claimed in any preceding claim, comprising a drive mechanism for driving rotation of the shaft, the shaft being axially moveable relative to the drive mechanism to disengage the shaft from the drive mechanism.
12. Apparatus as claimed in claim 11, comprising a driven member located on the shaft for connecting the shaft to the drive mechanism, and wherein the stop member is arranged to abut the driven member.
13. Apparatus as claimed in claim 12, wherein the stop member extends about the driven member.
14. Apparatus as claimed in claim 13, wherein the stop member comprises a shoulder extending radially inwardly towards the shaft and the driven member comprises a radially extending abutment surface facing the shoulder of the stop member.
15. Apparatus as claimed in any one of claims 12 to 14, comprising a bearing located between the stop member and the driven member.
16. A domestic appliance comprising apparatus as claimed in any one of the preceding claims.
17. A domestic appliance as claimed in claim 16, comprising a casing, the apparatus being moveable relative to the casing to allow a user to move the stop member relative to the shaft.