GB2491383A

GB2491383A - Epicyclic gearbox with orthogonal slow-speed drive

Info

Publication number: GB2491383A
Application number: GB1109226.9A
Authority: GB
Inventors: David Lowes
Original assignee: Kenwood Ltd
Current assignee: Kenwood Ltd
Priority date: 2011-06-02
Filing date: 2011-06-02
Publication date: 2012-12-05
Anticipated expiration: 2031-06-02
Also published as: GB201109226D0; GB2491383B

Abstract

An epicyclic gearbox 60, for stand mixers for the kitchen, provides a planetary drive shaft 66 which is orientated in a first direction, and a slow-speed, rotary drive outlet shaft 72 orientated in an orthogonal direction to the first direction. The drive shaft 66 is driven by a planet gear 67 which meshes with a fixed ring gear 68 and a sun gear on an underside of compound gear 63. Planet gear 67 reacts against the ring gear 68 to rotate planet carrier 65 around ring gear 68. Rotation of the planet carrier 65 causes central drive shaft 64 to rotate which drives bevel pair 70, 71 and the drive outlet shaft 72. The planetary drive shaft 66 is used to drive tools designed for mixing ingredients in a bowl, and the rotary drive outlet shaft 72 is used to drive attachments intended to perform mincing operations and the like. Reference is also made to a stand mixer incorporating or comprising the epicyclic gearbox 60.

Description

I

EPICYCUC GEARBOX PROVIDING PLANETARY DRiVE AND ORThOGONAL SLOW-SPEED DRIVE The present invention relates to epicyclic gearboxes, and it relates especially though not exclusively to such gearboxes for use in stand mixers for the kitchen. It relates more particularly to an epicyclic gearbox providing not only a planetary drive orientated in a first direction, but also a slow-speed, rotary drive outlet orientated in an orthogonal direction.

The invention also encompasses a stand mixer incorporating such a gearbox.

In the context of a stand mixer, the planetary drive would be orientated vertically and used to drive tools designed for mixing ingredients in a bowl, and the rotary drive outlet would be orientated horizontally, and used to drive attachments intended to perform mincing operations and the like.

Typically, stand mixers conform to a somewhat C-shaped structure, with a pedestal base on which a bowl can be supported, an upright housing portion and a head portion which extends from the top of the upright portion overhead of the bowl and carries a gearbox, in this case an epicycic gearbox, which presents a downwardly-directed drive outlet, located directly above the bowl and capable of imparting the aforementioned planetary mixing action to one or more tools attached to the drive outlet and suspended into the bowL The primary drive is usually provided by a heavy-duty electric motor which may be housed either in the upright portion of the mixer housing or in the head portion thereof and is conveyed to the epicyclic gearbox by belts and/or gears, or in general in any manner that may be convenient for the prevailing construction and circumstances.

It is convenient to use an epicyclic gearbox arrangement to implement the planetary drive required by a stand mixer, since such arrangements are robust and compact and can deal comfortably with the torque and speed requirements of such mixers. However, it is also desirable for the stand mixer to provide an additional rotary drive outlet, horizontally directed and accessible at the outwardly-facing end of the head portion of the mixer, to drive attachments, such as meat mincing attachments, which need to be driven relatively slowly but with high torque. Most stand mixers provide at least one other drive outlet too, again with differing speed/torque capabilities, for driving blenders and the like, but this invention primarily concerns the provision of the aforementioned slow-speed rotary drive outlet as a derivative from the epicyclic gearbox, so the other drive or drives will not be further discussed herein. It is stressed moreover that the present invention can be used in stand mixers with any number of drives.

lt is important, for reasons such as economy of construction, compactness and power transmission efficiency amongst others, to derive the slow-speed rotary drive from the planetary drive gearbox. Problems arise, however, when attempting to provide a slow speed rotary outlet from an epicyclic gearbox which is also used to provide a planetary drive.

These problems arise primarily because the epicyclic gearing configuration that is normally employed in a stand mixer to optiniise the planetary drive performance requires at least one planet gear to mesh with and revolve around a central sun gear which is driven from the motor, and a fixed outer ring gear which encircles the sun and planet combination, concentric with the sun gear and meshing with the planet gear(s). The at least one planet gear is supported on a carrier which allows free rotation of the planet gear around its own axis and around that of the sun gear whilst preventing any axial or radial movement, in the case where there are multiple planet gears, the planet carrier also determines their angular separation around the central sun gear.

It is a characteristic of such an epicyclic gearbox, where the ring gear is fixed and the sun gear is driven, that the maximum gear reduction is obtained between the sun gear and the planet carrier.

The sun gear is usually accessible at a convenient location on the gearbox to provide a drive for the slow-speed outlet. However, if the drive to the slow-speed outlet were to be taken directly from the central drive shaft/sun gear of the epicyclic gearbox at a 1:1 ratio then, in order to provide the required slow-speed rotation, the motor speed itself would need to be restricted so that it would almost certainly not be operating at maximum torque or efficiency. Such an arrangement would also disadvantageously require either additional electrical interlocking, to sense usage of the slow-speed drive and automatically reduce the motor speed accordingly, or the manual actuation of a motor speed control by a user of the stand mixer.

if on the other hand an additional gear reduction stage were to be provided, this would require the use of a larger gearbox to accommodate a large diameter gear and/or the provision of the slow-speed drive on a shaft offset from the horizontal centre-line of the head portion of the stand mixer, neither of which is desirable.

in principle, therefore, it might be considered advantageous to arrange the gearbox so that the drive to the horizontal slow-speed outlet is taken from the planet carrier, rather than the sun gear, since the planet carrier is already turning at (or very close to) the desired speed, so that no additional gear reduction stage is required and the motor can be operated at its optimum power and efficiency. However, unlike the sun gear, the planet carrier is not readily accessible at a location that is convenient to provide power for the slow-speed drive.

One way of deriving the slow-speed drive from a planet carrier is to rotate the head portion of the food mixer so that the axis of rotation of the planet carrier is made as near horizontal as possible. However, this arrangement has drawbacks in that it not only imposes significant constraints on the design of the food mixer, but also has the effect of increasing the height of the slow-speed outlet, making it more difficult for example to load ingredients into the hopper of the food mincer and potentially reducing the stability of the machine in use.

Another approach, disclosed in FR-A-2844442, is to enlarge the planet carrier so that it envelops the entire epicyclic gearbox in order to transfer drive to a horizontal outlet via a bevel gear mounted on its external surface. Drawbacks of this approach are that it is coniplex and results in the stand mixer having a much bulkier head portion, which reduces access to the bowl for the addition of ingredients or observation of the contents being processed.

it is one object of this invention to provide an epicyclic gearbox used to provide a planetary drive orientated in a first direction and a slow-speed rotary drive oriented in a direction orthogonal to the first, wherein the rotary drive is driven from a planet carrier component of said gearbox but without the drawbacks mentioned above associated with current arrangements.

The invention seeks among other things to provide a horizontal, slow-speed outlet driven by the rotation of the planet carrier within a vertically orientated epicyclic gearbox in a compact overall gearbox package.

According to the invention from one aspect there is provided an epicyclic gearbox presenting a planetary drive outlet orientated in a first direction; the gearbox comprising a sun wheel formed with a central aperture therethrough and means for driving said sun wheel about an axis passing through said aperture and aligned substantially parallel to said first direction; the gearbox further comprising a shaft, fixed at one end to a planet carrier and rotating therewith at the planet carrier speed; said shaft extending through the central aperture in the sun wheel, being free to rotate relative to said sun wheel, and bearing at its free end a driving component for a slow-speed rotary drive outlet orientated substantially orthogonally to the said first direction.

By this means, the invention provides a compact and efficient system for delivering, for example, a horizontally orientated slow-speed rotary drive together with a vertically orientated planetary drive capability, by making the planet carrier motion of an epicyclic gearbox accessible by way of a shaft that can protrude through, and freely rotate within, a through aperture formed centrally of a driven sun wheel component of the gearbox.

The said gear component carried at the upper end of said vertical shaft is preferably a bevel gear configured to mesh with a further bevel gear forming part of said slow-speed rotary drive outlet.

it is preferred that the first-mentioned bevel gear and the further bevel gear are configured to provide a gearing ratio close to 1:1. Preferably, however, the gearing differs slightly from a precise 1:1 ratio, so that the same teeth on the two gears are not permanently in mesh with one another.

in a preferred embodiment of the invention, the epicyclic gearbox is provided with a stationary and fixed ring gear configured to mesh with at least one planet gear carried by said planet carrier and rotated by said sun wheel, thereby to cause said planet carrier to rotate around the axis of the sun wheel.

According to the invention from another aspect, there is provided a stand mixer comprising an epicyclic gearbox used to impose a planetary mixing action on one or more tools suspendable vertically into a bowl from a head portion of the mixer, wherein an additional, horizontally-directed slow-speed rotary drive outlet is provided at said head portion and driven from a planet carrier component of said gearbox, wherein the gearbox incorporates a driven sun wheel component configured to drive the planet carrier in rotation about the sun wheel axis and characterised in that the sun wheel is formed with an aperture passing centrally therethrough and in that the planet carrier supports a vertical shaft passing through and rotatable within said aperture; said vertical shaft being fixedly secured to said planet carrier so as to rotate therewith and carrying at its upper end a gear component of said slow-speed rotary drive.

is in order that the invention may be clearly understood and readily carried into effect, one embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 shows, in perspective view, a stand mixer in accordance with one example of the invention; Figure 2 shows the stand mixer of Figure 1 from a frontal elevation; and Figure 3 shows, in vertical cross-sectional view, a gearbox in accordance with one embodiment of the present invention.

Referring now to Figures 1 and 2, in which corresponding features carry the same reference numbers, a stand mixer 10 is generally "C' shaped, and comprises a pedestal 20, which supports a bowl platform 30, an upright housing portion 40 and a head portion 48 which extends from the top of the upright portion to overly the bowl platform 30. An electric motor (not shown) is mounted either in the upright portion 40 of the mixer 10, or in the head portion 48, depending (inter alia) upon the type of motor used, the desired operating characteristics of the mixer 10 and ergonomics/design criteria. In any event, gearing (not shown) is provided to convey the motive power supplied by the motor to a plurality of drive outlets to which various tools can be attached to perform a wide variety of tasks in the kitchen.

In this particular example, them is provided a high-speed blender drive outlet behind covers 4!, a slow-speed mincer drive outlet behind cover 42 and a planetary drive, intended for food mixing, overhead of the bowl location, at 43, although it will readily be appreciated that more, fewer and/or different drive outlets can be provided in accordance with desired functionality of the stand mixer. The planetary drive and the slow-speed drive are, in this example, provided by an epicyclic gearbox in accordance with the inventioL and as will be described in more detail hereinafter.

A shanked mixing tool, attached as is conventional, to a socket 44 of the outlet 43, will depend in use into a mixing bowl placed on the bowl platform 30, and is configured to rotate about both the axis of the socket 44 and the central axis 45 of the outlet 43, thus performing a planetary mixing action. The necessary relationships between the relative shapes and dimensions of the bowl and the mixing tool to ensure thorough and repeatable mixing of ingredients are well known and established in use over many years.

As shown in Figures 1 and 2, the stand mixer 10 is, in this example, provided with a pair of latches 31, 32 within a recess 33 provided in the bowl platform 30, which latches co-operate with components on the base of the bowl to form a bayonet latching system which ensures firm and ready location of the bowl on its platform. Other latching systems, such as screw-threading for example, can be used as an alternative to bayonet latching if preferred.

The upright part 46 of the housing 40 is configured with a break line 47, to permit the top part 48 of the stand mixer to be hinged away from the platform 30 end of the pedestal part 20, in order to facilitate the insertion and removal of the mixing tools and the bowl.

The stand mixer 10 also incorporates electrical and mechanical user controls 51, 52 in conventional fashion.

Referring now to Figure 3, the epicyclic gearbox 60 according to this example of the invention comprises an input shaft 61 driven by a pulley and belt system (not shown) from the aforementioned electric motor (also not shown). A pinion gear 62 fixed to the input shaft 61 turns a compound gear 63, the underside of which forms the sun gear of the epicyclic gearbox 60. The compound gear 63 is formed with a central aperture 63a through which passes a central vertical driveshaft 64. The base of the central driveshaft 64 is locked to a planet carrier 65 which holds a planet shaft 66 and its associated planet gear 67. A ring gear 68 is fixed to the outer structure 69 of the gearbox 60. At the top of the central driveshaft 64 is a bevel gear pair 70, 71. The vertical bevel gear 70 is locked to and thus directly driven by the rotation of the central driveshaft 64 at the speed of the planet carrier 65 to which the shaft 64 is fixedly secured.

The horizontal bevel gear 71 is locked to and thus directly drives the slow-speed outlet shaft 72 which, when not in use, is concealed behind the cover 42 (see Figures 1 and 2).

In operation, drive from the motor rotates the input shaft 61 and its pinion 62 which in turn rotates the compound gear 63. The sun gear on the underside of the compound gear 63 rotates the planet gear 67 which reacts against the fixed ring gear 68 to rotate the planet carrier 65 around the ring gear 68. Rotation of the planet carrier 65 causes the central driveshaft 64, which protrudes through the aperture 63a, to rotate and therefore to drive in rotation the bevel gear pair 70, 71 and the output shaft 72.

The rotational speed of the slow-speed output shaft 72 is thus related to that of the planet carrier 65 by the gear ratio of the bevel gear pair 70, 71, which is typically close to but not exactly 1:1 to ensure that the same teeth on each gear are not always in-mesh with each other.

The sub-assembly comprising the planet carrier 65 and the driveshaft 64 is supported by bearings 73 and 74, whilst a bush 75 pressed into the aperture 63a in the centre of the compound gear 63 allows the driveshaft 64 to rotate freely within it and thus relative to the compound gear 63. ii

Claims

Claims: 1. An epicyclic gearbox presenting a planetary drive outlet orientated in a first direction; the gearbox comprising a sun wheel formed with a central aperture therethrough and means for driving said sun wheel about an axis passing through said aperture and aligned substantially parallel to said first direction; the gearbox further comprising a shaft, fixed at one end to a planet carrier and rotating therewith at the planet carrier speed; said shaft extending through the central aperture in the sun wheel, being free to rotate relative to said sun wheel, and bearing at its free end a driving component for a slow-speed rotary drive outlet orientated substantially orthogonally to the said first direction.
2. A gearbox according to claim 1, wherein said slow-speed outlet is orientated horizontally.
3. A gearbox according to claim I or claim 2, wherein said driving component carried at the upper end of said shaft comprises a bevel gear configured to mesh with a further bevel gear forming part of said slow-speed rotary drive outlet.
4. A gearbox according to claim 3, wherein the first-mentioned bevel gear and the further bevel gear are configured to provide a gearing ratio close to but not precisely 1:1, so that the same teeth on the two gears are not permanently in mesh with one another.
5. A gearbox according to any preceding claim, further comprising a stationary and fixed ring gear configured to mesh with at least one planet gear carried by said planet carrier and rotated by said sun wheel, thereby to cause said planet carrier to rotate around the axis of the sun wheel.
6. An epicyclic gearbox substantially as herein described and/or as shown in the accompanying drawings.
7. A stand mixer incorporating a gearbox according to any preceding claim.
8. A stand mixer comprising an epicyclic gearbox used to impose a planetary mixing action on one or more tools suspendable vertically into a bowl from a head portion of the mixer, wherein an additional, horizontally-directed slow-speed rotary drive outlet is provided at said head portion and driven from a planet carrier component of said gearbox, wherein the gearbox incorporates a driven sun wheel component configured to drive the planet carrier in rotation about the sun wheel axis and characterised in that the sun wheel is formed with an aperture passing centrally therethrough and in that the planet carrier supports a vertical shaft passing through and rotatable within said aperture; said vertical shaft being fixedly secured to said planet carrier so as to rotate therewith and carrying at its upper end a gear component of said slow-speed rotary drive.