PORTABLE PUMP

Abstract

A reciprocating air compressor arrangement includes a crank that drives a connecting rod and a piston within a cylinder. The connecting rod has a first end and a second end. The first end of the connecting rod is connected to the crank and the second end of the connecting rod is connected to the piston, with the crank provided to actuate the piston in a reciprocating motion within and relative to the cylinder so as to compress air within the cylinder. The reciprocating air compressor arrangement has a one-way flapper inlet valve allowing air to enter the cylinder, and a one-way outlet valve allowing compressed air to exit the cylinder. The inlet valve is biased to a partially open position.

Claims

1. A portable pump comprising: a reciprocating air compressor arrangement, the air compressor arrangement comprising: a crank that drives a connecting rod and a piston within a cylinder, the connecting rod having a first end and a second end, the first end of the connecting rod connected to the crank and the second end of the connecting rod connected to the piston, with the crank provided to actuate the piston in a reciprocating motion within and relative to the cylinder so as to compress air within the cylinder, the reciprocating air compressor arrangement having a one-way flapper inlet valve allowing air to enter the cylinder, and a one-way outlet valve allowing compressed air to exit the cylinder, wherein the inlet valve is biased to a partially open position; an electric motor having a drive shaft mounted to the crank, with the drive shaft rotatable about a drive shaft axis, and with the drive shaft axis at least substantially coaxially aligned with an axis of rotation of the crank; a control unit in electrical communication with the electric motor to control operation of the pump; a power supply in electrical communication with the control unit to supply power to the control unit and electric motor; the electric motor, the reciprocating air compressor arrangement, the control unit and the power supply each contained within a common housing; and an outlet fluidly connected to the outlet valve of the reciprocating air compressor arrangement for fluidly engaging with an object to be pumped.

2. A portable pump according to claim 1, wherein the cylinder comprises a cylinder head, and the outlet valve comprises an outlet port, with the outlet port extending through the cylinder head to allow for a flow of compressed air to exit the cylinder.

3. A portable pump according to claim 1, wherein the inlet valve comprises an inlet port, with the inlet port extending through the cylinder head to allow for a flow of air to enter the cylinder.

4. A portable pump according to claim 1, wherein the piston comprises a piston head, and the inlet valve comprises an inlet port, with the inlet port extending through the piston head to allow for a flow of air to enter the cylinder.

5. A portable pump according to claim 1, wherein during operation of the portable pump, the inlet valve is movable between the partially open position, a fully open position and a closed position.

6. A portable pump according to claim 5, wherein the portable pump is switchable between ON and OFF modes, and the inlet valve remains in the partially open position when the portable pump is in the OFF mode.

7. A portable pump according to claim 1, wherein the power supply is a rechargeable battery having a C rating of at least approximately 20, and capable of providing a maximum current of at least 4 Amps.

8. A portable pump according to claim 1, wherein the electric motor is a brushless DC motor having a motor diameter of between approximately 20 and 30 mm, and preferably approximately 23 mm.

9. A portable pump according to claim 1, wherein the pump has a total weight of less than 100 grams, and can pump up at least one bicycle road or commuter bike tyre to approximately 80 psi on a single charge.

10. A portable pump according to claim 1, wherein the housing has a length of between approximately 45 and 65 mm, a height of less than approximately 50 mm, and a width (or thickness) of approximately 25 mm.

11. A portable pump according to claim 1, wherein the outlet is provided on or mounted to the housing.

12. A portable pump according to claim 11, wherein the outlet comprises a collar extending outwardly from the housing, the collar comprising a valve receiving bore for receiving a valve of the object to be pumped.

13. A portable pump according to claim 1, wherein the outlet valve is a flapper valve or a check valve.

14. A reciprocating air compressor arrangement comprising: a crank that drives a connecting rod and a piston within a cylinder, the connecting rod having a first end and a second end, the first end of the connecting rod connected to the crank and the second end of the connecting rod connected to the piston, with the crank provided to actuate the piston in a reciprocating motion within and relative to the cylinder so as to compress air within the cylinder, the reciprocating air compressor arrangement having a one-way flapper inlet valve allowing air to enter the cylinder, and a one-way outlet valve allowing compressed air to exit the cylinder; wherein the inlet valve is biased to a partially open position.

15. A reciprocating air compressor arrangement according to claim 14, wherein the cylinder comprises a cylinder head, and the outlet valve comprises an outlet port, with the outlet port extending through the cylinder head to allow for a flow of compressed air to exit the cylinder.

16. A reciprocating air compressor arrangement according to claim 14, wherein the inlet valve comprises an inlet port, with the inlet port extending through the cylinder head to allow for a flow of air to enter the cylinder.

17. A reciprocating air compressor arrangement according to claim 14, wherein the piston comprises a piston head, and the inlet valve comprises an inlet port, with the inlet port extending through the piston head to allow for a flow of air to enter the cylinder.

18. A reciprocating air compressor arrangement according to claim 14 wherein, during operation of the air compressor arrangement, the inlet valve is movable between the partially open position, a fully open position and a closed position.

19. A reciprocating air compressor arrangement according to claim 18, wherein the air compressor arrangement is switchable between ON and OFF modes, and the inlet valve remains in the partially open position when the air compressor arrangement is in the OFF mode.

20. A reciprocating air compressor arrangement according to claim 14, wherein the outlet valve is a flapper valve or a check valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] It will be convenient to hereinafter describe preferred embodiments of the invention with reference to the accompanying figures. The particularity of the figures is to be understood as not limiting the preceding broad description of the invention.

[0030] FIG. 1 is a schematic side view of a prior art air compressor arrangement.

[0031] FIG. 2 is a schematic side view of another prior art air compressor arrangement.

[0032] FIGS. 3a to 3c show further schematic side views of a prior art air compressor arrangement similar to that of FIG. 1, with FIGS. 3a to 3c showing an operating sequence of the air compressor arrangement.

[0033] FIGS. 4a to 4c show schematic side views of another prior art air compressor arrangement, with FIGS. 4a to 4c showing an operating sequence of the air compressor arrangement.

[0034] FIGS. 5a to 5d show schematic side views of an air compressor arrangement according to a first embodiment of the present invention, with FIGS. 5a to 5d showing an operating sequence of the air compressor arrangement.

[0035] FIGS. 6a to 6d show schematic side views of an air compressor arrangement according to a second embodiment of the present invention, with FIGS. 6a to 6d showing an operating sequence of the air compressor arrangement.

[0036] FIG. 7 is an isometric view of a portable pump according to the present invention. FIG. 7 also provides a size comparison of the portable pump of the present invention with the applicant's existing FUMPA™ and miniFUMPA™ portable pumps, which are the respective subjects of allowed U.S. patent application Ser. No. 15/750,130 and U.S. Pat. No. 10,837,433.

DETAILED DESCRIPTION

[0037] As referred to previously, there is growing demand for portable, battery powered bicycle pumps in the cycling industry. Current electric bike pumps are generally large and cumbersome, weighing around 500 grams. These pumps are far too big to mount onto a bicycle or fit in one's pocket. The applicant's miniFUMPA™ pump (the subject of U.S. Pat. No. 10,837,433) is the smallest electric pump currently available. However, it has a weight of around 200 grams, a length of approximately 75 mm, a height of approximately 70 mm (not including the nozzle) and a thickness (or width) of around 30-35 mm. This makes it too big to fit into a pocket, or a small handbag. As stated previously, there is a need for a truly pocket-sized pump, having a weight of around 100 grams, a height of less than 50 mm and thickness of around 25 mm. At this weight and dimension, the pump could be taken on practically any bicycle journey in a user's pocket or very small carry bag/handbag. Commuter cyclists would find such a pump appealing as it could be placed in their bag or pocket on their way to work.

[0038] To realize such a small pump, all aspects of the pump need to be miniaturised. Electric bike pumps generally consist of a reciprocating air compressor, a motor to drive the air compressor, a battery for use as the power source, control circuitry and enclosure to house all parts. The bulk of the size and weight of a pump comes from the air compressor, motor and battery. Therefore, in order to reduce the size and weight, these three components must be made as small as possible.

[0039] FIG. 1 shows the basic design of a prior art reciprocating air compressor 10. The main components are the crank 12, driven by the motor (not shown), which moves the piston 14 up and down within a cylinder 16 via a connecting rod 18. A one-way flapper inlet valve 20 (having an inlet port 20a) brings air into the cylinder 16 when the piston 14 is moving in a downwards direction, whilst a one-way flapper outlet valve 22 (having an outlet port 22a) allows compressed air to be removed from the top 24 of the air compressor 10 when the piston 14 is moving in an upwards direction. The Force (Fc) required to drive the piston 14 up to the top of the cylinder 16 can be estimated as follows:

[00001]$\begin{array}{cc}{F}_c=F_m\cos \left({\theta }_1\right)& \left(1\right)\end{array}$$\mathrm{Where}$$\begin{array}{cc}{F}_m=\frac{\tau }{L_c}& \left(2\right)\end{array}$

Where τ is the torque the motor can provide.

[0040] Reducing parameters such as cylinder diameter (and therefore piston diameter), or crank size (and therefore length L.sub.c) will reduce the volume of air being compressed, which in turn reduces the compression ratio. This will undesirably result in an increase in pump up time and the maximum pressure the pump can achieve. A certain amount of reduction can be tolerated depending on how long a user can wait for their tire to be pumped, or what pressure they need. However, too much reduction in these dimensions will result in a pump that is less useful. Further to this, inlet and outlet valves need to be mounted to the air compressor, and these can only be reduced in size within practical limits before their performance is reduced to their detriment.

[0041] One parameter that can be reduced is the length of the connecting rod 18, as shown in the prior art air compressor of FIG. 2. Reducing the length of the connecting rod 118 in FIG. 2 (compared to the length of the connecting rod 18 in FIG. 1) reduces the overall height of the air compressor, whereby L.sub.2<L.sub.1. However, in doing so θ.sub.2>θ.sub.1, and so a smaller crank force F.sub.c is generated for the same amount of motor torque. This reduction in F.sub.c is detrimental, especially when the designer is attempting to design an air compressor 10/110 that can be driven by the smallest motor possible. Miniature motors (both brushed and brushless) are inefficient in nature, and they generally only achieve high torques when run at maximum speeds. Therefore, on start-up, the available motor torque is a design constraint. For small motors, available motor torque is generally proportional to motor diameter. As motor diameter is one of the main parameters affecting the pump thickness dimension, there are difficulties in trying to provide enough torque to rotate the air compressor 10/110, whilst using a motor of suitable small diameter.

[0042] Larger air compressors overcome this motor torque limitation by obviously selecting a larger sized motor. Further to this, designers will often design a low-pressure volume directly after the outlet valve so that on motor start-up, the air compressor is pumping air into a volume that is essentially at zero-gauge pressure. This is achieved through use of non-return and/or exhaust valves. Due to size constraints however, such a design is not achievable on a miniature air compressor.

[0043] FIGS. 3a to 3c illustrate an operating sequence of prior art air compressor 210. Air compressor 210 is very similar to air compressor 10 shown in FIG. 1. FIG. 3a shows the air compressor 210 in its at-rest position. It can be seen that in the at-rest position the one-way flapper inlet valve 220 (having an inlet port 220a) and the one-way flapper (or reed) outlet valve 222 (having an outlet port 222a) are both biased into their respective closed positions. As shown in FIG. 3b, when the piston 214 moves in a downwards direction Y1 within the cylinder 216 the negative air pressure temporarily created within the cylinder chamber 217 causes the inlet valve 220 to open, thereby allowing the inflow of air into the chamber 217. The inlet valve 220 closes once the piston 214 reaches its lowermost position within the cylinder 216. When the piston 214 moves in an upwardly direction Y2 (see FIG. 3c) within the cylinder 216, the inlet valve 220 remains temporarily closed, but the increasing pressure within the chamber causes the outlet valve 222 to open, through which compressed air is expelled from within the chamber 217.

[0044] FIGS. 4a to 4c illustrate an operating sequence of prior art air compressor 310. The operation of air compressor 310 is similar to that of air compressor 210 shown in FIGS. 3a to 3c. However, one fundamental difference between air compressors 210 and 310 is that the inlet valve 220 of air compressor 210 is mounted in the cylinder head 216a, whereas the inlet valve 320 of air compressor 310 is mounted within the piston head 314a.

[0045] It can be seen in FIG. 4a that in the at-rest position the one-way flapper inlet valve 320 and the one-way flapper outlet valve 322 are biased into their respective closed positions. As shown in FIG. 4b, when the piston 314 moves in a downwards direction Y3 within the cylinder 316 the negative air pressure temporarily created within the cylinder chamber 317 causes the inlet valve 320 to open, thereby allowing the inflow of air into the chamber 317. The inlet valve 320 closes once the piston 314 reaches its lowermost position within the cylinder 316. When the piston 314 moves in an upwardly direction Y4 (see FIG. 4c) within the cylinder 316, the inlet valve 320 remains temporarily closed, but the increasing pressure within the chamber causes the outlet valve 322 to open, through which compressed air is expelled from within the chamber 317.

[0046] Reciprocating air compressors 210/310 of the type shown in FIGS. 3a to 3c and 4a to 4c generally rely on reed (or flapper) one-way valves to let air into and out of the cylinder. These valves are usually manufactured from high fatigue strength thin steel material. They are generally cantilevered, flat in shape and move up and down depending in the pressure differential they experience on each of their surfaces.

[0047] If an air compressor like the one shown in FIGS. 3a to 3c (or that shown in FIGS. 4a to 4c) is connected to a bicycle tire that is already at a high pressure (50 psi for example), then on motor start-up, a significant motor torque might be required to turn the crank from a stationary position and to open the outlet valve 222. Further to this, as reed valves are simple structures that often do not have the luxury of a high-quality seals, the outlet valve 222 can leak, causing pressure inside the cylinder 216 to be equal to the pressure inside the tire. This results in very high start-up torques being needed to start the compression process. If the motor cannot provide the torque, the motor stalls and can result in motor and/or circuit burnout.

[0048] To overcome this issue, the applicant has found that this increase in motor torque requirement can be offset by changing the shape of the inlet valve 220 to that shown in FIGS. 5a to 5d (and that shown in FIGS. 6a to 6d).

[0049] One embodiment of the invention is now shown in FIGS. 5a to 5d, wherein a reciprocating air compressor arrangement 410 of a portable bike pump 400 (see FIG. 7) according to one embodiment of the present invention is illustrated.

[0050] The arrangement 410 includes a crank (not shown) that drives a connecting rod 418 and a piston 414 within a cylinder 416. The connecting rod 418 has a first end (not shown) and a second end 421. The first end of the connecting rod 418 is connected to the crank and the second end 421 of the connecting rod 418 is connected to the piston 414. The crank is provided to actuate the piston 414 in a reciprocating motion within and relative to the cylinder 416, so as to compress air within the cylinder 416. The arrangement 410 has a one-way flapper inlet valve 420 with an inlet port 420a allowing air to enter the cylinder 416, and a one-way flapper outlet valve 422 (with an outlet port 422a) allowing compressed air to exit the cylinder 416. It is to be appreciated that, if desired, the outlet valve 422 need not be a flapper valve. For example, the outlet valve could be a check valve. FIG. 5a shows the arrangement at rest, whereby the piston 414 is stationary within the cylinder 416. It is important to appreciate from FIG. 5a that the inlet valve 420 is biased into a partially open position when the arrangement 410 is at rest. The fact that the inlet valve 420 is partially open when the arrangement 410 is at rest is considered unique to the present bike pump; and is also considered unique to the applicant's inventive air compressor arrangements.

[0051] The inlet valve 420 is, during use, movable between the partially open position shown in FIGS. 5a and 5c, the closed position shown in FIG. 5d, and the fully open position shown in FIG. 5b.

[0052] The outlet valve 422 is movable between the closed positions shown in FIGS. 5a to 5c, and the open position shown in FIG. 5d.

[0053] FIG. 5a shows the air compressor 410 in its at-rest position, with the one-way flapper inlet valve 420 in a partially open position, and the one-way flapper outlet valve 422 in a closed position. As shown in FIG. 5b, when the piston 414 moves in a downwards direction Y5 within the cylinder 416 the negative air pressure temporarily created within the cylinder chamber 417 causes the inlet valve 420 to further open, thereby further allowing the inflow of air into the chamber 417. The outlet valve 422 remains in its closed position. The inlet valve 420 returns to its partially open position when the piston commences moving in the upwards direction Y6 shown in FIG. 5c, whereby a small amount of air can still escape through the inlet port 422a. However, when the piston 414 approaches its uppermost position in the cylinder shown in FIG. 5d, sufficient air pressure within the cylinder 416 is created to fully close the inlet valve 420, and also open outlet valve to allow pressurized air to exit through outlet port 422a.

[0054] From the above comments, it is to be understood that the shape of the inlet valve 420 is designed so that it is encouraged to leak, which is counter the design of conventional valves. This is achieved by manufacturing the inlet valve 420 with a curve so that it sits open in its at-rest state. When the motor is stationary (and the piston 414 is therefore stationary) air inside the cylinder 416 is maintained at zero-gauge pressure. Even if the outlet valve 422 is leaking when engaged onto a bicycle tire, the curve in the inlet valve 420 ensures air can escape from the cylinder 416 to the atmosphere.

[0055] On motor start-up, if the piston 414 is moving in the downward direction, the inlet valve 420 will further open to ensure air is entering the cylinder 416. Once the piston 414 moves upwards (as shown in FIG. 5c) air will initially leak through the inlet valve 420. This greatly reduces the torque requirements on the motor to turn the crank. Once the motor gets to its top running speed (and therefore able to provide its highest level of torque), the applicant has found that the inlet valve 420 would close fully when the piston 414 was moving in an upward position (shown in FIG. 5d), desirably resulting in adequate air compression during the reciprocating process.

[0056] The applicant has found that utilizing curved inlet valves allowed brushless out-runner motors as small as 23 mm in diameter to power 14 mm diameter air compressor pistons/cylinders. The applicant did find a trade-off, however. A curved inlet valve 420 resulted in a reduction in maximum achievable pressure. For small volume tires (for example, road bicycle tires, 700×23 c, approximately 800 ml in volume), a pressure of only about 80-90 psi is achievable; while for larger commuter bike tires (700×28 c up to 700×35 c tires) a pressure of about 70-80 psi is achievable. These pressures are less than what is achievable with traditional flat reed valve designs (120 psi and greater). However, as commuter bicycle tires only require pressures of up to 80 psi, this method to reduce the required motor torque is a plausible solution.

[0057] One of the other constraints of a pocket-sized pump is the size of the battery. Motor driven air compressors require large currents, and so high discharge lithium polymer batteries are commonly used to supply power. However, there is a limit to the amount of current that can be drawn from a battery. The battery must be able to handle the high currents required to drive the compressor, without affecting is performance, or worse, being damaged due to excessive current draw.

[0058] The rate (C) at which a battery can be safely discharged is dependent on both the maximum discharge current (I) that the battery experiences, and the battery's capacity (ρ). These three variables are related as follows:

I=ρC

[0059] Battery sizes of similar dimension to miniature motors (23 mm) can be manufactured with a C rating of approximately 20 C. This is less than the current design requirements of the pump the subject of U.S. Pat. No. 10,837,433. For high discharge lithium batteries currently available in sizes close to the diameter of the motor requirements of a miniature pump, 200-300 mAh batteries are an option. Therefore, from the equation above, a maximum current of only 4-6 Amps of current is available from such small batteries.

[0060] The applicant has found that if a flat inlet valve (such as of the prior art types illustrated in FIGS. 1 to 4c) is used, it was almost impossible to achieve tire pressures greater than 50 psi without motor stall occurring. Further to this, currents exceeding 6 Amps were common. However, using a curved inlet valve resulted in tire pressures exceeding 80 psi and currents of less than 5 amps were possible. The provision of a curved inlet valve ensured pressures were achievable whilst ensuring batteries were not being damaged due to excessive current draw.

[0061] FIGS. 6a to 6d illustrate an operating sequence of an air compressor arrangement 510 according to another embodiment of the present invention. The operation of air compressor arrangement 510 is similar to that of air compressor arrangement 410 shown in FIGS. 5a to 5d. One fundamental difference between air compressor arrangements 410 and 510 is that the inlet valve 420 of air compressor arrangement 410 is mounted in the cylinder head 416a, whereas the inlet valve 520 of air compressor arrangement 510 is mounted within the piston head 514a. In other respects, air compressor arrangements 410 and 510 are the same.

[0062] FIG. 7 shows an embodiment of micro bicycle tire pump 400 according to an embodiment of the present invention in isometric view.

[0063] Advantageously, the pump 400 is extremely light weight, with a total weight of less than 100 grams. The pump 400 is capable of pumping up at least one bicycle road or commuter bike tire to approximately 80 psi on a single charge.

[0064] The pump 400 includes a novel reciprocating air compressor arrangement generally of the type previously described.

[0065] The pump 400 includes a housing 402. Within the housing 400 (and therefore not clearly shown) there is provided a power supply in the form of a high discharge lithium battery, and an electric motor having a drive shaft that connects directly to the reciprocating air compressor arrangement. In this regard, the drive shaft is rigidly mounted to the crank, with the rotation axes of the drive shaft and the crank aligned.

[0066] The electric motor is in the form of a brushless DC motor having a motor diameter of between approximately 20 and 30 mm and, more preferably, approximately 23 mm.

[0067] Although not shown in FIG. 7, the housing of pump 400 includes a charge port. The charge port allows the use of an external charger to charge the pump's internal battery.

[0068] The pump 400 includes a compressed air outlet 404 for engagement with a bicycle tire valve (not shown). The outlet 404 is fluidly connected to the outlet valve of the reciprocating air compressor arrangement. The outlet 404 is mounted on or to the housing 402, and includes a valve receiving bore 406 for receiving a valve of the tire (or other object) to be pumped. As the pump 400 is so small, it easily fits between the spokes of a bicycle wheel without use of a hose extending between the outlet 404 and the tire valve.

[0069] The pump 400 further includes a control unit in electrical communication with the electric motor to control operation of the pump and the power supply. The control unit may be a printed circuit board that consists of control circuitry that turns the motor ON and OFF via a switch and monitors the battery's voltage.

[0070] In operation, the portable pump 400 is turned on by a user via switch 408. Once turned on, the electric motor starts running which, in turn, rotates the drive shaft. The rotating drive shaft turns/rotates the crank, causing the connecting rod and piston to reciprocate axially within the cylinder. One-way flapper inlet and outlet valves of the air compressor arrangement ensure that air is compressed inside the cylinder and forced through the outlet 404. This process is carried out many times a second as the piston axially reciprocates within the cylinder. The unique design of the inlet valve, whereby it is biased into a partially open position (including when the pump is initially turned ON), desirably avoids the need for the motor to overcome an initially high start-up torque which can easily result in motor and/or circuit burnout.

[0071] Advantageously, the design of the portable pump 400 allows it to be manufactured small enough so that it can be mounted directly onto a tire valve. Indeed, the pump 400 can be considered to be of a micro size when compared to existing pump designs, including the applicant's pumps the subjects of U.S. Pat. No. 10,837,433 and U.S. patent application Ser. No. 15/750,130. This means that no additional hose or fittings are required to transfer the compressed air to the tire, as the pump can fit between most conventional 700 mm diameter bicycle wheel spoke configurations and directly onto the tire valve, thereby further reducing the size and weight of the pump 400. The pump 400 is manufactured without a gearbox or outlet hose, and so this enables the pump 400 to be of a very small size when compared to existing pump designs. The pump 400 has a length only in the order of approximately 45 to 65 mm, a height of less than approximately 50 mm and a width (or thickness) of approximately 25 mm. These small dimensions allow the pump to fit easily into a cyclist's jersey pocket or small handbag.

[0072] FIG. 7 is useful in that it provides size comparisons between the applicant's new pump 400, and their existing (and market leading) pumps 500, 600, the subjects of U.S. Pat. No. 10,837,433 and allowed U.S. patent application Ser. No. 15/750,130, respectively. It is important to appreciate that the smaller dimensions of their latest pump 400 compared to their existing pumps 500, 600 hasn't been achieved simply by miniaturizing components of the pumps 500, 600 such that they fit into the smaller housing 402 of pump 400. Instead, the smaller size of pump 400 was the result of considerable re-design and invention by the applicant and, in particular, the complete re-design of the inlet valve of the air compressor arrangement.

[0073] Finally, it is to be appreciated that the applicant's unique inlet valve design could conceivably be applied to any conventional air compressor arrangement. This, in turn, may desirably obviate the need for a given air compressor arrangement to require an unloader valve, which is a common failure point.

[0074] It is to be understood that various alterations, modifications and/or additions may be introduced into the construction and arrangement of the parts previously described without departing from the spirit or ambit of this invention.