GB2504073A - A drive mechanism for a hand pump with folding crank handle - Google Patents

Abstract

A hand pump comprises a rotary to linear displacement conversion mechanism having driver and driven discs 13, 14 for driving a piston 10 within a barrel 11 and a crank handle 103 extending transversely of the barrel 11 and connected to an input drive stem 30 to enable manual rotation thereof. The crank handle 103 is pivotally mounted to pivot block 102 and a grip 104 is pivotally mounted to an end of the crank lever 103. When not in use, the crank handle 103 is articulated in a radial plane so that it can be folded away alongside the barrel 11 in a channel like recess 108. Displacement is effected by rotation of driver discs 13 on stem 30 which act to cam apart interleaved driven discs 14. The stem 30 is of non-circular cross section to cause rotation of the driver discs 13 whereas the driven discs are constrained against rotation by making the barrel cross section and driven discs 13 non-circular. The inner barrel wall is smooth to facilitate good sealing.

Description

Drive assembly and hand pump The present invention relates to drive assemblies and to hand pumps employing such assemblies. In particular, the invention relates to assemblies employing rotational to linear displacement conversion mechanisms.

Background of the invention

In European patent EP2210014B1, a rotary to linear displacement conversion mechanism is described in which a stack of alternately mounted driver and driven discs are mounted for translation on a common central axis. The discs have complementarily shaped ramped surfaces, which, in one state, are snugly inter-engaged so that the stack is of minimum length. The driven discs are constrained against rotation so that when the driver discs are rotated together, the resulting camming action of the ramped surfaces of the discs on each other causes the stack to expand. The driver discs are coupled for rotation together in such a way as to permit them to separate linearly. A return spring restores the stack to its original length when the ramped surfaces ride over each other and the two types of discs return to their fully inter-engaged state.

The coupling mechanism for coupling the driver discs together consists of projections extending axially from each driver disc through bores in the intermediate driven discs to locate slideably in a recess in a proximate driver disc so that rotational drive can be transmitted between the driver discs while at the same time permitting translation.

The driven discs are constrained against rotation by means of peripheral lugs, which engage in grooves in a surrounding support structure, for example a cage, barrel or other casing.

One possible application of such a displacement mechanism to a hand pump is described in which the disc stack and return spring are contained within a fixed length barrel and the rotation is provided by means of a crank handle, connected to a drive shaft with a profiled end portion which engages a first driver disc.

Linear action hand pumps, for example for bicycle tyre inflation, are known in which the pump handle may be pivotally mounted on the piston shaft. In US patent 6817060 entitled, "Collapsible handle device for inflator", a pivoted handle is also slotted so that it can be turned through 180° to partially enclose the shaft and it can then be slid over the pump barrel for compactness. For normal linear pumping action, the handle is firstly rotated in line with the barrel to its extended position.

A linear action bicycle pump with a folding T-handle known as the Blackburn Mammoth AnyValve is also shown on the website http://www.blackburndesign.com/pumps.html

Disclosure of the Invention

The prior art does not show a compact version of a hand pump employing a rotary action handle. Accordingly, in a first aspect, the present invention provides a hand pump comprising: an elongated barrel defining a central axis; a fluid inlet and outlet; a piston reciprocable within the barrel to draw fluid into the inlet and to pump fluid to the outlet; a displacement conversion mechanism within the barrel having an input portion rotatable about the barrel axis and an output portion connected to the piston so as to cause the piston to reciprocate in response to rotation of the input portion, and a crank extending transversely of the barrel and connected to the input portion of the displacement mechanism at one end to enable manual rotation thereof, characterised in that: the crank is articulated in a radial plane with respect to the barrel axis so that it can be folded away alongside the barrel when not in use Preferably, the crank includes a grip portion at its distal end and is doubly articulated to permit deployment of the grip portion transversely of the crank when the crank is extended transversely of the barrel.

Preferably, the crank is attached to the input portion of the displacement mechanism by means of a first pivot pin, the grip portion being attached to the remainder of the crank by a second pivot pin. Alternative forms of looser linkage may be employed with detent or locating features to fix the operational position. The grip may be attached by a ball joint, allowing it to rotate in use and without the necessity to constrain it to a precise angular orientation.

In the preferred arrangement however, the first pin allows the crank to rotate through 270° until it abuts a stop on the input portion of the displacement mechanism. Also, the second pin allows the grip portion to rotate through at least 900 until it abuts a stop on the crank.

The fold away feature of the crank handle enables the handle to be of substantially the same length as the barrel. This allows the application of maximum torque to the displacement conversion niechanism in comparison with a shorter fixed cross handle.

For compactness, the barrel is preferably provided with an external channel-like recess, into which the crank handle can be folded.

In like manner, preferably, the crank handle is itself relieved to accommodate the grip portion when stowed.

It will also be noted that the projecting piong and bore coupling arrangement of the prior art is a relatively complex arrangement for coupling driver discs together for rotation, while permitting them to separate and translate along an axis, and also limits the amount of achievable offset between driver and driven discs. Accordingly, from a second aspect, the present invention provides a drive assembly for driving an output element along a linear axis, the drive assembly including a plurality of driver discoidal elements and a plurality of diiven discoidal elements mounted alteinately along said linear axis, each discoidal element having a ramped surface, the ramped surfaces of adjacent elements being complementarily shaped and opposed so that when in contact and completely interengaged they form a stack of minimum length; coupling means foi coupling the drivei discoidal elements together for rotation while permitting them to translate along the axis; the diiven elements being mounted in such a way as to permit translation along the axis while preventing their rotation about the axis, whereby rotation of the driver elements causes the elements to separate by camming action of their interengaged ramp surfaces so as to produce an extension of the stack corresponding to the cumulative separations of the drivei and driven elements, such extension being transmitted to the output element; and characterized in that: the coupling means includes a rotatable drive shaft of non circular cross section; the driver elements each have a central aperture of complementary shape to the non circular cross section of the drive shaft and are slideably mounted thereon; and the driven elements each have a central aperture sufficient to permit rotation of the drive shaft within their central aperture as well as translation along the drive shaft.

The use of a drive shaft instead of the direct driver disc-to-disc couplings of the prior art offers a more robust method of rotating the discs apart and has been noted above can enable greater disc to disc offsets to be achieved because of the potentially greater strength of a coupling via a common shaft. Of course, using a fixed length drive shaft does mean that the disc stack cannot extend beyond the length of the shaft.

Drive assemblies according to this second aspect of the invention may be readily applied to hand pumps but may also be used with powered pumps. The pumped fluid may be any gas, such as air or any liquid. Besides pump applications, the principles of the drive assembly may be applied to other applications including actuators for shut off valves, print carriage drivers and linear rams.

Although various drive shaft cross sections, such as square are possible, the preferred drive shaft is elliptical in cross section, with the central aperture of the driven elements being circular and having a diameter at least equal to the major axis of the elliptical cross section of the drive shaft.

Many applications, such as pumps, will require a casing containing the stack of elements, the drive shaft and the output element. In such cases, the driven elements and casing are preferably shaped to engage so as to prevent rotation of the driven elements while permitting translation.

Preferably, the assembly includes return means, typically a spring, for restoring the stack to its minimum length upon further rotation of the drive shaft.

Further according to the second aspect of the invention, the assembly may be employed in a pump in which a barrel having a fluid inlet and outlet contains a piston output member within the barrel, continuous rotation to the drive shaft causing reciprocation of the piston to draw fluid into the inlet in one phase of shaft rotation and to pump fluid to the outlet in a second phase of shaft rotation.

Preferably, in the case just mentioned, the piston divides the barrel into first and second chambers, each chamber having an inlet and an outlet for fluid such that, when fluid is pumped to the outlet of one of said chambers, further fluid is drawn into the inlet of the other of said chambers. Rather than having completely distinct inlets and outlets for each chamber, external parts may be shared but the internal paths to the two chambers will then separate.

Additionally, the prior art shows a pump having a barrel in which the driven discs and piston are constrained against rotation by peripheral lugs engaging with complementary features of the barrel. Such a non-circular cross section does not facilitate a good seal for the piston within the barrel. Accordingly, from a third aspect, the present invention provides a pump comprising a barrel; a piston, slideable within the barrel; a drive assembly for driving the piston along a linear axis of the barrel, the drive assembly including a plurality of driver discoidal elements and a plurality of driven discoidal elements mounted alternately along said linear axis, each discoidal element having a ramped surface, the ramped surfaces of adjacent elements being complementarily shaped and opposed so that when in contact and completely interengaged they form a stack of minimum length; coupling means for coupling the driver discoidal elements together for rotation while permitting them to translate along the axis; the barrel, the driven elements and the piston having complementary non-circular axial cross sections so as to permit translation of the driven elements along the axis while preventing their rotation about the axis, whereby rotation of the driver elements causes the elements to separate by camming action of their interengaged ramped surfaces so as to produce an extension of the stack corresponding to the cumulative separations of the driver and driven elements, such extension being transmitted to the piston; characterized in that: the axial cross section of the barrel is smooth.

This lack of discontinuity in the barrel wall facilitates an improved seal between the piston and the barrel and enables the use of a seal ring around the piston which can conform closely to its cross sectional shape and to the inner wall of the barrel.

Preferably, the cross section of the barrel is elliptical which is a convenient shape for gripping in the case of a hand pump, though other smoothly curved shapes can be envisaged.

However, it should be noted that this aspect of the invention is not limited to hand pumps or to air pumps but may be employed in other fluid pumping devices.

In pumps according to this third aspect of the invention, the piston can advantageously be formed with one ramped surface complementarily shaped to an opposed surface of the terminal driver element of the stack so that the piston is driven further along the axis by camming action of the terminal driver element on the piston.

Brief Description of the Drawings

The invention will now be described by way of example only with reference to preferied embodiments theieof, as illustrated in the accompanying diawings in which: Figure 1 is a cross section through a first embodiment of a hand pump and drive assembly according to the invention, including a crank mechanism shown in a stowed position; Figure 2 shows a further partial cross section of the hand pump and drive assembly of Figure 1, with the crank mechanism deployed and iotated to complete a fiist stroke; Figure 3 shows a side elevation of a diiver disc employed in the assembly of Figure 1; Figure 4 shows a front elevation of the driver disc of Figure 3; Figure 5 shows a side elevation of a diiven disc employed in the assembly of Figure 1; Figure 6 shows a front elevation of the driven disc of Figure 5; Figure 7 shows a side elevation of an elliptical driven disc employed in a second embodiment of a hand pump and drive assembly according to the invention; Figure 8 shows a front elevation of the driven disc of Figure 7; Figure 9 shows a cross section through the pump of Figure 1, taken on the line A-A ofFigure2; Figure 10 shows a similar cross section through the second embodiment of the hand pump according to the invention; Figure 11 is an exploded perspective view of the pump portions of the assembly of Figure 1, illustrating the airflow; Figure 12 is a front elevation of one face of a rear cap shown in Figure 11; Figure 13 is a front elevation illustrating the hidden face of an end cap shown in Figure 11; Figure 14 is an exploded view of the piston assembly of the hand pump of Figure 1; Figure 15 is an exploded view of a piston assembly of the second embodiment of the invention partly illustrated in Figure 7; Figure 16 is a perspective view of the pump of Figure 1 with the handle stowed; Figure 17 is a perspective view of the pump of Figure 1 with the handle in a partially deployed position; and Figure 18 is a perspective view of the pump of Figure 1 with the handle fully deployed.

Detailed Description of the Invention

A hand pump according to the invention is shown in Figures 1 and 2. The hand pump also comprises a drive mechanism according to the invention. The drive mechanism includes a rotational to linear displacement conversion mechanism for driving a piston assembly 10 along a pump barrel 11 to expel air under pressure from an outlet 12 at one end thereof.

The displacement conversion mechanism is similar to that illustrated in EP 2210014 and consists of a stack of alternating driver and driven discs 13 and 14 respectively.

The discs are profiled to be of undulating form as shown in Figures 3 to 6, in which high regions or ridges 15 and 16 are separated by low regions or valleys illustrated by concentric shading lines. As in EP 2210014, both types of discs can translate along an axis 17 of the barrel or casing but the driven discs are constrained against rotation.

In Figure 1, the discs are nested, that is, they are completely inter-engaged, to form a stack of minimum length. The driver discs are coupled for rotation together about the axis and, as a result of such rotation, exert a camming force on the driven discs, as the high regions come into alignment, forcing them to separate from their adjacent driver discs. The stack thus expands to a fully extended state, as shown in Figure 2, forcing the piston 10 along the barrel thus expelling air from outlet 12.

As rotation of the driver discs continues, the discs revert to their nested state allowing a compression spring 18 to return the piston towards the right hand end of the barrel.

The compression spring is housed in a housing 19.

The discs are made of nylon 6-6, which offers a sufficient combination of rigidity and low friction to enable the camming action to take place by direct contact between driver and driven discs. Alternatively, they can be made of pressed stainless steel.

To the extent described so far, the principles of operation are identical to those of the mechanism and pump of EP 2210014. However, the illustrated pump according to the present invention has several advantages. One fundamental difference, which will be described in more detail below in connection with Figure 11, below, is that the pump is double acting and expels air through outlet 12 on both the disc driven stroke and the return spring driven stroke. The portion of the barrel containing the disc stack constitutes an upper chamber 20 and the portion containing the return spring constitutes a lower chamber 21. The two chambers vary in size in dependence on the position of the piston assembly 10.

A very important difference from EP 2210014 is the driving and coupling together of the driver discs 13. As shown in the cross section of Figure 9, taken on line A-A of Figure 2, the driver discs 13 are mounted on a drive stem or shaft 30, which is mounted for rotation within the barrel 11. The drive stem has an elliptical cross section and the driver discs, as also shown in Figure 4, each have a central aperture 31 of substantially the same dimensions so as to fit snugly yet slideably on the drive stem 30. Thus, when the drive stem 30 is rotated by a manual crank mechanism 100, as will be described further with reference to Figure 2, the driver discs are also rotated to exert the camming force on the driven discs 14. As seen in Figures 1 and 2, the drive stem also includes an integral flange 32 at the crank end, which is profiled on one side in the same manner as the driver discs and which acts on the rightmost driven disc 14 of the stack. The drive stem also includes a circular section extension 33, adapted to be coupled to the crank mechanism 100.

As shown in Figures 5 and 6 and also in Figure 9, the driven discs 14 each have a circular central aperture 34 whose diameter substantially equals the major axis of the elliptical apertures 31 in the driver discs, with sufficient clearance to allow unimpeded rotation of the drive stem 30.

The driven discs 14 are each formed with three ears or lugs 35 which locate in internal grooves 36 extending along the barrel 11 and visible in Figures 1, 2 and 11.

These act to prevent rotation of the driven discs within the barrel while still allowing them to translate along the barrel. It will be noted from Figures 1 and 2 that the right hand face of the piston assembly 10 is formed with a profile complementary to that of the leftmost driver disc 14, which thus exerts a camming action on the piston to cause a small further leftward movement.

The pneumatic aspects of the hand pump will now be described further with reference to Figures 11 to 13 of the drawings. Essentially, conduits for air intake and outlet to and from both the upper and lower chambers are formed in the barrel and its end pieces so that air is drawn in to the expanding chamber on one stroke and, at the same time, is expelled from the contracting chamber to the outlet 12. One-way valves ensure that air flows only in the required direction.

A schematic airflow diagram is shown in Figure 11, which omits certain components, such as the drive stem 30, the spring 18 and the piston assembly 10 for reasons of clarity. The central portion of barrel 11 has also been omitted to save space. As shown by the broad arrows 50, representing airflow into and out of the upper chamber 20, when the piston 10 is driven manually to the left by expansion of the disk stack, as shown in Figure 2, air is drawn into the upper chamber 20 of the pump.

The air enters by way of a gap 101 between a crank pivot block 102 and a rear cap 53, best seen in Figure 1.

Concentrating first on the upper chamber 20, air enters the upper chamber via a bore 52 in the rear cap 53, at the rightmost end of the barrel 11. It continues via a one-way valve 54 of the "duck bill" type, located in a rear seal 55 inward of the rear cap 53, SO as to fill the chamber 20 with air as the chamber expands. When the piston 10 returns to the right under the restoring action of spring 18, air is forced from the upper chamber under pressure to the outlet 12 in the following way.

As shown by further arrows 50, compressed air passes through a bore 57 in the rear seal 55 to a channel conduit 58 on the inner face of rear cap 53 (as more clearly shown in Figure 12). The air is prevented from escaping from the upper chamber via the bore 52 by valve 54. The conduit 58 effectively reverses the direction of outgoing air and directs it back through a one-way valve 60 and a short bore 61 in rear seal 55 to a long bore 59, running the length of the barrel 11. Reverse flow is prevented by means of the valve 60. The rear cap 53 and rear seal 55 each have a rubberized surface sufficient to prevent leakage from the air path formed by bores 59, 61 and conduit 58. From the bore 59, the compressed air from the upper chamber passes through spring housing 19 to an end cap 70. A cowl 86 in the spring housing diverts the air into a recessed conduit 71 (Figure 13) for conducting the air to a bore 72 (Figures 1 and 2) leading to outlet 12.

The intake and expulsion of air from the lower chamber 21 follows similar principles and works in anti-phase to the upper chamber 20 so that air is drawn into the lower chamber at the same time as it is expelled from the upper chamber. Thus, when the piston 10 is driven to the right, under the action of return spring 18 as shown in Figure 1, air is drawn into the lower chamber 21! initially through the same gap 101 between the rear cap 53 and the crank pivot block 102, as indicated by arrows 51 representing airflow through the lower chamber. A conduit 81 (see Figure 12) on the inner face of the rear cap 53 and a bore 82 in the rear seal 55 lead the air to a bore 83 extending along the barrel 11 and through spring housing 19 to end cap 70. The direction of flow is reversed by a further recessed conduit 74, on the inner face of the end cap (see Figure 13) into which air is diverted by a further cowl 87 on the spring housing. From there it passes through a one-way valve 75 into the lower chamber 21, containing the spring 18.

When the piston 10 is driven to the left, as the drive stem is manually rotated by crank mechanism 100, compressed air is expelled from the lower chamber as indicated by further arrows 51. The expelled air passes straight through a bore 85 in the spring housing 50 and a one-way valve 76 in the end cap to a bore 77 (see Figures 1 and 13), leading to outlet 12. A ridge 88 in the spring housing 19 locates in a complementary groove 78 in end cap 70 so that the bores in each component, such as 85 and 77, are correctly aligned. Again, sealing to prevent side leakage is effected by rubberizing the opposed faces of the spring housing and end cap and clamping them together.

Thus, because of the dual action arrangement using both chambers 19 and 20, air is continually pumped from outlet 12 as the drive stem 30 rotates. The pump action is exceptionally efficient as the disc stack expands considerably in a linear direction for a relatively limited rotation. This is determined by the relative height of the ridges in relation to the thickness of the discs.

In order to achieve effective pumping action, it is of course necessary to seal the piston assembly 10 well in the barrel to prevent leakage between the two chambers.

The assembly and its seals will now be described in detail with reference to Figures 1 and 14. Essentially, the assembly 10 consists of a piston seat 90 and piston cover 91 between which are sandwiched two interlocking piston seals 92 and 93.

To prevent leakage between the upper and lower chambers around the drive stem 30, the small gap between the seals and the rotatable drive stem is further sealed by means of an 0-ring 94. At their outer edge, another 0-ring 95 provides an extra seal to the barrel wall.

Because the 0-ring 95 cannot extend into the grooves 36 in the barrel wall for locating the ears 35 of the driven discs, three further small 0-rings 96 are located on stubs formed in the piston seat to prevent leakage via the grooves 36, only one of which is visible in Figure 1.

A somewhat simpler piston sealing arrangement is shown in the alternative pump embodiment illustrated in Figures 7, 8, 10 and 15. In other respects, the operation of the pump is the same as that of the pump described above with reference to the other Figures.

The alternative arrangement employs an elliptical barrel 211, as shown in Figure 10, elliptical driven discs 214, as shown in Figures 7 and 8 and an elliptical piston assembly 210, as shown in Figure 15. The driven discs 214 have high regions 216 which correspond to regions 16 (Figure 6) and which can be forced apart by the camming action of rotatable driver discs with which they are interleaved in a stack.

The driver discs are identical to those of Figure 3 and 4, that is, they are circular and able to rotate freely within barrel 211. They are driven by an elliptical drive shaft in the same way as those of Figures 1 and 2 which shaft passes through circular apertures 234 in the centre of the driven discs, without interference.

The camming action takes place because the driven discs 214 and piston assembly 210 are constrained against rotation by virtue of their elliptical shape being complementary to the cross section of the barrel 211.

The smooth nature of the barrel wall, without discontinuities, facilitates the employment of a simple 0-ring type elliptical seal 295, as seen in Figure 15, between a piston cover 291 and a piston seat 290, both forming pad of assembly 210, and the wall of the barrel 211. The seal around the drive shaft is provided by a smaller elliptical 0-ring 294 trapped between piston seals 292 and 293.

Thus, by changing the cross sectional shape of the barrel in this way, only two ring seals are needed in comparison to the five employed in the embodiment of Figures 1, 2 and 14. It is also easier to achieve better sealing with the larger axis rings than with the small diameter ring seals 96 for sealing grooves 36 in Figures 1 and 2.

A further important feature of the hand pumps illustrated, which is substantially the same for both embodiments, is the crank mechanism 100. This is illustrated in Figures 1 and 2 but also in the perspective views of Figures 16 to 18, which show it in different states of deployment.

The mechanism consists of three primary components! namely: the crank pivot block 102, a crank handle 103 and a grip 104. The crank pivot block, which is at the right hand end of the pump, is fixed to the drive stem 30 by means of a stem fixing pin 105.

The crank handle 103 is itself pivotally mounted in the pivot block 102 by means of a pivot pin 106 and the grip 104 is, in turn, pivotally mounted on the end of the crank handle by means of a further pivot pin 107. The crank handle is relieved to form a recess 112 towards its outer end to accommodate the grip 104 in a compact manner.

This doubly articulated arrangement enables the crank handle and grip both to be folded neatly away into a larger channel-like recess 108 along the upper barrel, as shown in Figure 1 and 9.

From this stowed position, as shown in Figure 16, the handle and grip may be rotated clockwise in a radial plane, as indicated by the broad arrows in Figures 1 and 17, to a fully deployed position, as shown in Figures 2 and 21. The crank handle 103 rotates through a maximum 01270° until stopped by the abutment of shoulder portion 110 with the base 111 of crank pivot block 102. The grip 104 may then be rotated through approximately 90° or slightly more until its inner corner portion 113 engages the stop surface constituted by the edge 114 at the outer corner of recess 104.

From the fully deployed position, the grip may be held firmly and the crank rotated to work the pump. After the pumping action is complete, the handle components stow away alongside the barrel, locating almost invisibly in the outer channel 108 thereof.

The compactness and smooth extelior of the mechanism make the pump easily attachable to bicycle frames.

A fuither advantage of the pump design is that the crank handle can be integial to the pump yet of substantially the same length as the barrel, allowing increased torque to be applied to overcome the resistance to rotation caused by expansion of the disc stack. This is important if a high ratio of ridge height to disc thickness is employed to achieve maximum piston displacement for a given rotation of the hand