Espresso machine pressure gauge

Abstract

A pressure gauge for a mechanically actuated espresso machine, for example, a lever or screw-based system allows the operator to determine the pressure applied to the coffee grounds and hot water in a

Description

Field of the Invention The present invention relates to mechanical espresso machines, in particular to pressure measurement within the brew chamber of such machines. Background of the Invention Coffee is one of the world’s most popular drinks, with approximately 2 billion cups consumed per day globally. Many coffee drinks are based on the espresso; which is a small dose of strong coffee brewed by flowing hot water under pressure through a compacted bed of ground coffee. When making espresso, an important variable to control, and thus measure, is the pressure of the water. Current espresso machines either use a conventional pressure gauge (which is hydraulically connected to the pressurised fluid) or forgo the pressure measurement altogether. On some machines, fitting a conventional pressure gauge can be challenging. There may not be space in the grouphead and fitting the gauge closer to the boiler may not provide an accurate measurement in the grouphead due to pressure loss in the system pipes. Another disadvantage of a separate pressure gauge is that an extra entrance needs to be made into the pressure chamber to connect the gauge to the fluid. This adds extra complexity to the processes of manufacturing and making the system leak-tight. There is also the possibility for water to stagnate in this small channel with consequent effects on taste and health. In the case of mechanically actuated machines, such as a lever or screw-based system, the operator has to apply a force to a handle, which is coupled to a piston in a cylinder. Hence, as a force is applied to the handle, the piston is moved in a cylinder, which pressurises the water between the piston and coffee. The present disclosure exploits the fact that the force applied to the piston can be correlated to the pressure in the chamber. In some cases, the handle charges a spring which applies a predefined pressure to the water; the present disclosure is not suited to these types of machines and neither is it suited to machines which generate pressure with an electric pump. The invention is suitable for closed or open boiler machines, or machines where the water is heated in a kettle and poured into the cylinder separately. 01 07 25 Summary of the Invention The pressure gauge operates such that when a force is applied to a handle or handles to generate pressure in the cylinder, parts of the mechanical system flex as the force is transferred to the piston. More force generates more deformation, which equates to a higher pressure in the cylinder. Nevertheless, the deformation of the system will typically be small and thus too insensitive to allow a direct readout of system deformation. This invention encompasses the concept of mechanical accentuation of the elastic deformation of some part of the mechanical system to read out pressure on a calibrated scale. These examples are intended to illustrate the invention but not limit its scope. Whilst the focus of the patent is a mechanically actuated espresso machine, the concept is also transferrable to other applications in which a pressure is manually applied through a handle mechanism, such as manual injection moulding machines, manual hydraulic pressure testers, force measurement on an arbor press or a pump. A person skilled in the art should be able to generate alternative constructs to the same effect using these guideline principles. Brief Description of the Drawings Figure 1 is a perspective view of the pressure gauge and the proximal end of the handle bar. This concept is suited to a lever espresso machine. Figure 2 is a side view of the distal end of the handle bar, relating to the same example as figure 1. Figure 3 is a perspective view of the pressure gauge based on a geared mechanism. This concept is suited to a screw espresso machine. Figure 4 is a perspective view of the pressure gauge based on a pin-and-slot mechanism. This concept is suited to a screw espresso machine. Detailed Description In figure 1, a handle bar 1 comprising a tube forms the lever which transfers the force from the user to the linkage mechanism of the particular espresso machine. Only the proximal end of the handle bar 1 is shown in figure 1. The distal end of the handle bar 1 is the handle of the lever, which the user grasps when operating the lever. The tube may be circular or polygonal in crosssection. Alternatively, the handle bar 1 may be solid and the disclosed mechanism mounted to the exterior of the handle bar 1. The handle bar 1 is designed to be able to flex slightly when force is 01 07 25 applied but not so much as to generate a noticeable deformation from the user’s perspective. A reference bar 2 is fixed at the distal end of the handle bar 1 but remains mechanically isolated up the length of the handle bar 1. Thus, as the user applies force to the handle end of the handle bar 1, the reference bar 2 moves relative to the handle bar 1 as the reference bar 2 is not subjected to flexure. The reference bar 2 is shaped to clear the remainder of the mechanism. In this case, a cut out 3 provides clearance for the indicator disc 5. The end of the reference bar 2 has a slot 4, which engages with a pin 8, which in turn is fixed to the indicator disc 5. The indictor disc 5 is attached to a pivot pin 9. The pivot pin 9 may be threaded 6 into the indictor disc 5 to allow easy assembly of the mechanism. The pivot pin 9 moves freely in a body to which the handle tube 1 is also attached. From a global frame of reference, the handle bar 1 flexes, yet the mechanism is better visualised from the frame of reference of the handle bar 1, where the proximal end of the reference bar 2 flexes; the pivot pin 9 and the proximal end of the handle bar 1 remain stationary in cartesian space, although note the pivot pin 9 is free to rotate. As the reference bar 2 moves relative to the handle bar 1, the indicator disc 5 rotates. A witness mark 7 moves and its alignment with graduations on a calibrated scale 10 indicates the pressure in the brew chamber of the espresso machine. The graduated scale 10 is attached or forms part of the body to which the proximal end of the handle bar 1 is affixed. The graduated scale 10 may be flat, where the angular displacement of the indicator disc 5 is maintained to a level where parallax error is acceptable. Alternatively, the graduated scale 10 may be curved to remove parallax error. The indicator disc 5 need not necessarily take the form of a disc. For example, an L-shaped construct, where the upper section of the ‘L’ forms the pointer may be used. The distal end of the handle bar 1 is shown in figure 2. The distal end of the reference bar 2 runs through the centre of a plug 11. A section of the reference bar 2 may protrude from the plug 11 to allow longitudinal and rotational adjustment of the reference bar 2 prior to fixing it with screws 12, 13. The screws 12, 13 also allow adjustment of the reference bar 2 by loosening one screw and tightening the opposing screw. The reference bar may bend into the plug cavity 14 during the adjustment process. This adjustment process allows easy zeroing of the pressure gauge. The reference bar 2 is held axial relative to the handle bar 1 by a bore 15 in the plug 11 which is equal in diameter to the reference bar 2. Additional screws may be added to allow adjustment in other planes. Figure 3 relates to another manifestation of the present disclosure better suited to a screw-based espresso machine. The crank 16 and handle 17 assembly are fixed onto a leadscrew with a grub screw 18. The leadscrew is inserted into the crank bore 19. Structural flexibility is engineered into 01 07 25 the crank 16 in this construct by means of reducing the stiffness locally, which is achieved by a thinned region 20. This may also be achieved by varying the material properties in the crank 16 or with a hollow construct, as shown in figure 1. One approach to varying the crank 16 material properties may be replacing the thinned region 20 with an insert of a different material. A plate 21 is attached to the crank 16, for example via screws inserted through holes 22 in the plate 21. A sector of a gear 23, which may also be approximated as a rack, meshes with a gear 24, with a pivot pin 25 anchored to the crank 16; alternatively, the pivot pin 25 may be anchored to the gear 24 and the pivot bearing is located in the crank 16 instead. The gear 24 is affixed to the pointer element 26, which may be cranked to clear the plate 21 holding screws. The end of the pointer element may be, but is not limited to, the shape of a ring 27, an arrow or a point. The pressure gauge is calibrated such that when the pointer aligns with the leadscrew centre, or the centre of rotation of the crank 16, the target pressure is achieved in the espresso machine brew chamber. Alternatively, a calibrated scale, as shown in figure 1 may be affixed to the crank 16 or form the end of the pointer element 26. In the latter instance, the scale may be formed on a transparent of translucent material with a witness mark beneath it located upon the centre of rotation of the crank 16. The flexure of the crank 16 is exaggerated due to the gear assembly located upon the upper face of the crank 16. The fewer teeth the gear 24 has, the larger the flexural exaggeration will be. The holes 22 in the plate 21 may be enlarged or slotted to allow adjustment of the meshing between the end of the plate 21 and the gear 24 as well as zero or target pressure adjustment. An alternative example suitable for a screw-based espresso machine is shown in figure 4, where rather than using gears to exaggerate the crank 16 deformation, a slot 28 in the pointer element 29 locates with a pin 30 affixed to a plate 31. The pointer element 29 rotates about pivot point 32. 01 07 25

Claims

1. A flexure-based pressure gauge configured to measure pressure in a piston-compressed espresso machine, which is implemented as part of a manual handle, lever or crank, used to apply force to the piston, comprising an elastically flexing handle bar and a reference bar which is not subject to flexure, wherein the pressure gauge magnifies the elastic strain in said handle due to the force applied to said handle, providing deflection of an indicator, which is calibrated to the hydraulic pressure in the espresso machine chamber.

2. A flexure-based pressure gauge according to any preceding claim, which is mounted on or inside a handle bar designed for a lever espresso machine.

3. A flexure-based pressure gauge according to any preceding claim which is mounted on or inside a handle bar designed for a screw-operated espresso machine.

4. A flexure-based pressure gauge according to any preceding claim wherein the pointer movement is accentuated by means of a pin-in-slot mechanism in which the pin is fixed to or comprises an element which becomes the moving indicator.

5. A flexure-based pressure gauge according to claims 1-3 wherein the pointer movement is accentuated by means of meshed gears in which one of the gears is fixed to or comprises an element which becomes the moving indicator.

6. A flexure-based pressure gauge according to claims 1-3 wherein the pointer movement is accentuated by means of a reference bar which is longer than the handle bar.

7. A flexure-based pressure gauge according to claims 1-3 and 6 wherein the reference bar comprises a plurality of elements, in which one of the elements is pivoted about a point fixed to the handle bar and the elements are mechanically coupled near this pivot point in the direction of flexure.

8. A flexure-based pressure gauge according to claim 7 wherein the mechanical coupling is provided using meshed gears, in which the gears are either fixed to their respective reference bar elements, form part of the reference bar elements or both.

9. A flexure-based pressure gauge according to claim 7 wherein the mechanical coupling is provided with a pin-in-slot mechanism.

10. A flexure-based pressure gauge according to any preceding claim wherein adjustment of the zero point or pressure calibration can be achieved by altering the position of the reference bar relative to the handle bar.

11. A flexure-based pressure gauge according to any preceding claim wherein the handle bar comprises a solid bar of round or polygonal cross section, a tube or both.

12. A flexure-based pressure gauge according to any preceding claim wherein the handle bar cross section is varied in geometry, material or both along its length.LO CXI13. A flexure-based pressure gauge according to any preceding claim wherein the reference bar cross section is varied in geometry, material or both along its length.

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