GB1580293A

GB1580293A - Pepper mill

Info

Publication number: GB1580293A
Application number: GB1468678A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-04-14
Filing date: 1978-04-14
Publication date: 1980-12-03

Description

(54) PEPPER MILL (71) I, JOHN GRAHAM STANFORD, a British subject, of The Wyndham Arms, Clearwell, Near Coleford, Gloucestershire, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to pepper mills. A pepper mill is to be understood to mean a device for grinding peppercorns or any other spice or other substance in the form of hard grains or seeds of similar size to peppercorns; and references herein to peppercorns should be construed accordingly.

According to the invention, a pepper mill comprises a housing having an internal surface of revolution defining a longitudinal axis, and a rotor having an external surface of revolution rotatable about the axis, the said surfaces defining between them a gap which converges longitudinally so that at one end of the gap the rotor surface is closely adjacent to the housing surface, the said surfaces having co-operating milling teeth which are helical on one of the surfaces and generally longitudinal on the pother.

Preferably at least one of the two surfaces is frustoconical.

According to a preferred feature of the invention, the teeth of at least one of the surfaces diminish in radial depth towards the said end of the gap; and in a preferred arrangement these are helical teeth of the rotor.

An embodiment of the invention will now be described, by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a sectional plan view of a handoperated pepper mill in a preferred form according to the invention, taken on the plane I-I in Figure 2; Figure 2 is a partly cut-away front elevation taken on the plane II-II in Figure 1; and Figure 3 is a composite sectional view of the rotor of the same mill, the top half of the Figure being a half-section at the left hand end (plane A-A, Figure 1), while the bottom half is a half-section at the plane B-B, Figure 1.

The pepper mill shown in Figures I and 2 consists essentially of a fixed hollow housing 1, a rotor 2 mounted in the housing, and a handle 3 for turning the rotor.

The housing 1 has a hollow body 6 having an internal surface 4 which is a surface of revolution defining a horizontal axis 5 of the mill. In this example the housing surface 4 is frustoconical, subtending a cone or apex angle of about 8 degrees. At the smaller end of the body 6 are mounting brackets 7 by which the mill can be fixed to a wall.

The interior of the housing body 6 constitutes a milling chamber 12, being closed at its smaller end by an integral end wall 8 having a coaxial bearing 9, and at its larger end by a removable plate 10, having another bearing 11 which is also coaxial with the body. The internal surface 4 has longitudinally extending milling teeth 13, which are typically arranged on a circumferential pitch of about 5 mm at the larger end of the milling chamber.

The rotor 2 has a body 14 with end shafts 15 and 16 which are free to rotate in the bearings 9 and 11 respectively, the handle 3 being mounted on the shaft 16. The rotor body 14 has an external surface 17 which is a surface of revolution, in this example frustoconical and subtending a cone angle of about 16 degrees. The rotor is arranged so that, when in position, its surface 17 is convergent in the same direction as the housing surface 4. Thus the gap 18, surrounding the rotorbodyand resulting from the difference in cone angle between rotor and housing, is convergent towards the larger end of the rotor body, at which the latter is very closely adjacent to the housing surface 4 in the transverse plane intersecting the end 19 of the gap 18 (Figure 1). The gap 18 subtends, in any diametral plane thereof, an angle G which is here about 4 degrees.

The rotor surface 17 is formed with helical milling teeth 20. In this example the teeth 20 are arranged on a circumferential pitch of about 5 mm at the larger end of the rotor body and at a helix angle of about 60 degrees. It will be noted that, at the larger end of the rotor, the pitch of the teeth 13 is approximately the same as that of the rotor teeth 20. These pitches vary over the length of the rotor 2 and milling chamber 12 by amounts which depend on the axial length of the rotor and on the cone angles; but at any place where rotor teeth are co-operating with housing teeth, the local circumferential pitch of the one and that of the other should differ by a factor of less than 2, and preferably less than 1.

Whereas the radial depth of each of the housing teeth 13 is constant over the length of the tooth, that ofeach rotor tooth 20 diminishes from the smaller end of the rotor body to the larger end. This is best seen from a comparison of the two halves of Figure 3, while from Figure 2 it can be seen that the depth of these teeth diminishes virtually to zero at the larger end of the rotor, i.e. at the end 19 of the gap 18.

The rotor 2 is mounted for axial floating movement in the bearings 9 and 11; but this movement is limited by a stop 21, which can be adjusted to determine the radial spacing between rotor and housing at the gap end 19, thus setting the degree of coarse or fine grinding to be effected by the mill.

In operation, peppercorns fall from a hopper 22, mounted on top of the housing body 6, through a hole 23 in the top of the latter and into the milling chamber 12. The hole 23 is over the rotor 2, but the peppercorns will tend to fall towards the smaller end of the latter. The rotor is turned in the direction indicated in Figure 2, and the peppercorns are progressively giound between the rotor teeth 20 and the housing teeth 13. The peppercorns tend to exert an axial thrust on the rotor, forcing it against the stop 21 and so stabilizing the size of the gap 18 and the consistency of grinding.

As the particle size is decreased by the grinding process, the pepper is urged along the grooves between the housing teeth 13, towards the end 19 of the gap 18, by virtue of the fact that the helices defined by the grooves between the rotor teeth extend in a trailing direction with respect to the direction of rotation. At the same time, because the rotor teeth decrease in radial depth, and consequently the surface area (24, Figure 3) of the grooves between the teeth not only increases but also becomes more nearly cylindrical, the pepper tends to be spread evenly over the rotor surface. This assists efficient and thorough grinding and also helps to prevent the teeth from becoming clogged with pepper.

Finally, the ground pepper falls from the rotor through a chute 25, formed in the housing body 6 and closed at the front by part of the plate 10.

A scraper blade 26, projecting forwards from the larger end face of the rotor body, prevents accumulation of ground pepper on the housing teeth in the zone between the rotor and the plate 10, by scraping it off so that it falls into the chute 25.

A number of variations, within the scope of the invention, canbe made on the mill described.

For example, it can be arranged in any known manner for mounting on a horizontal surface, e.g. by a releasable vacuum clamp or permanent fixing bracket on the underside of the housing body.

The mill need not be manually operated, but may if desired incorporate an electric motor, preferably coupled to the rotor through a suitable reduction gearbox. This may be especiallyuseful in a very large catering establishment, since an electric pepper mill of this kind can fill a pepper pot in a matter of seconds. To this end the motor is preferably controlled by a switch incorporating a timer, so that when a start button is pressed, the motor gives a single burst of the required duration, and is then switched off automatically. The switch may be arranged to be operated, in the manner well known to those skilled in automatic control of machines, by a pepper pot being placed beneath the chute, the latter being modified so that it funnels the pepper into the pot.

Although it is preferred that it be the rotor that has helical teeth, its teeth may be generally longitudinal while those of the housing are helical. The housing teeth may be formed with diminishing depth towards the narrow end of the gap surrounding the rotor, provided that this is so done that the radial distance between the rotor teeth and housing teeth at the narrow end of the gap can be kept sufficiently small.

The rotor teeth may then be of constant depth throughout their length. Indeed, although the provision of teeth of diminishing depth is preferred, the teeth of both the rotor and the housing may each be of constant depth over their length.

It will be realised that, provided a convergent coaxial gap is preserved around the rotor, either the rotor body or the bore of the housing may be cylindrical or of any other suitable shape. Alternatively, where both of the surfaces of revolution are of axially-convergent form (e.g. frustoconical), they may be so arranged that they converge in opposite axial directions. In such an arrangement the cone angles can be made the same as each other, i.e. equal to the convergence angle G of the gap.

In all cases, however, the mill is arranged so that peppercorns fed into the milling chamber towards the larger end of the gap will move towards the smaller end of the latter as they are ground.

Where generally longitudinal milling teeth are provided on a convergent surface of the mill, it is not essential that the peak of each tooth shall lie in a single diametral plane. For example, it may be more convenient to form the teeth in the internal surface of the housing in two or more sets of parallel teeth, each tooth of a set being at constant pitch with respect to its neighbour or neighbours in the set throughout its length. In such a case some of these teeth will then be helical, but on a helix angle which is very small with reference to the axial direction.

In place of the simple end stop 21, other forms of stop may be used: for example a suitable thrust bearing (preferably axially adjustable) may be substituted for the bearing 11. This is especially desirable where the mill is electrically operated or otherwise adapted for high-speed, repetitive operation.

The rotor may be separated from its shaft, and mounted thereon instead of being integral with two end shafts as described.

WHAT I CLAIM IS: 1. A pepper mill comprising a housing having an internal surface of revolution defining a longitudinal axis, and a rotor having an external surface of revolution rotatable about the axis, the said surfaces defining between them a gap which converges longitudinally so that, at one end of the gap, the rotor surface is closely adjacent to the housing surface, the said surfaces having co-operating milling teeth which are helical on one of the surfaces and generally longitudinal on the other.

2. A mill according to Claim 1, wherein the rotor surface is frustoconical.

3. A mill according to Claim 1 or Claim 2, wherein the housing surface is frustoconical.

4. A mill according to Claim 1, wherein both of the said surfaces are frustoconical and convergent in the same direction.

5. A mill according to Claim 4, wherein the cone angle of the rotor surface is larger than that of the housing surface.

6. A mill according to any preceding claim, wherein the said surfaces are of such shape that the said gap subtends at its said end an angle of4 degrees between them.

7. A mill according to Claims 5 and 6, wherein the cone angles of the rotor surface and the housing surface are 8 and 4 degrees respectively.

8. A mill according to any preceding claim, wherein the helical milling teeth are formed to a helix angle of 60 degrees.

9. A mill according to any preceding claim, wherein the pitch of the rotor teeth, and the pitch of the housing teeth at the said end of the gap, differ from each other by a factor no greater than one and a half.

10. A mill according to Claim 9, wherein the said pitches are substantially equal.

11. A mill according to any preceding claim, wherein the teeth of at least one of the said surfaces diminish in radial depth towards the said end of the gap.

12. A mill according to any preceding claim, wherein the rotor has helical teeth diminishing in radial depth towards the said end of the gap.

13. A mill according to Claim 11 or Claim 12, wherein the said radial depth is substantially zero at the said end of the gap.

14. A mill according to any preceding claim, wherein the rotor is mounted for axial floating movement with respect to the housing, and wherein adjustable stop means are provided for engaging the rotor to limit the extent of the floating movement, whereby to set the ground particle size.

15. A pepper mill substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. suitable thrust bearing (preferably axially adjustable) may be substituted for the bearing 11. This is especially desirable where the mill is electrically operated or otherwise adapted for high-speed, repetitive operation. The rotor may be separated from its shaft, and mounted thereon instead of being integral with two end shafts as described. WHAT I CLAIM IS:

1. A pepper mill comprising a housing having an internal surface of revolution defining a longitudinal axis, and a rotor having an external surface of revolution rotatable about the axis, the said surfaces defining between them a gap which converges longitudinally so that, at one end of the gap, the rotor surface is closely adjacent to the housing surface, the said surfaces having co-operating milling teeth which are helical on one of the surfaces and generally longitudinal on the other.

2. A mill according to Claim 1, wherein the rotor surface is frustoconical.