Patent Application
20220364554
This application claims priority to Australian Patent Application No. 2021901420, filed on May 13, 2021, which is incorporated herein by reference in its entirety.
The present invention relates to a reciprocating air compressor arrangement. The invention has particular application in the context of a portable, hand-held pump for filling objects with gases such as air and so will hereinafter generally be described in this context.
It is to be appreciated, however, that the invention is not limited to portable hand-held pumps. The invention may be applied to a range of air compressor sizes and designs, including those used in commercial, industrial and domestic applications.
Pumps used to fill objects to a high pressure typically incorporate a reciprocating air compressor. These types of compressors tend to be large and heavy in size and require an external power supply. This, in turn, makes such pumps difficult to transport and less useful if an external power supply is not readily available.
The above problems are exacerbated for cyclists who require portability, a pump that is light weight, and one that pumps up tires quickly. While some cyclists use carbon dioxide canisters (known as CO2 inflators), these canisters have a number of disadvantages, including the fact that they are intended for only a single use. Another problem is that they become very cold during use and may expose a user to potential burns, particularly on their hands and fingers.
Other pumping solutions include traditional manual hand pumps, often designed to be releasably mounted to and carried on a bicycle frame. These are light weight but are slow to use, in that they require a relatively large amount of time to inflate a tire.
While some portable, battery powered air pumps do exist, they tend to be of a relatively large size, cumbersome, of substantial weight (500 grams, or more), and are designed to be stand-alone. However, due to the recent advances in high discharge lithium batteries, small, high pressure compressors are starting to be realized. The Applicant's commercially successful FUMPA™ bike pump, the subject of foreign patents, and recently allowed U.S. patent application Ser. No. 15/750,130, describes a portable pump, whereby a reciprocating air compressor is actuated by a brushless motor via a gear assembly, and is powered by a high discharge lithium battery. The components are all contained within a thermally conductive housing thereby improving the thermal efficiency of the compressor.
A potential limitation noted by the Applicant in the pump of allowed U.S. patent application Ser. No. 15/750,130 is that it is impractical for a cyclist to carry the unit in their cycling jersey pocket, given the relatively large size and the weight of the unit. The relatively large size is mainly due to the use of a bulky gear assembly to drive the compressor via the brushless motor. As the pump is too large to directly engage onto a bicycle tire's valve, a hose and fitting arrangement is provided to supply compressed air from the unit to the tire. Further to this, the inflation time of the pump described in allowed U.S. patent application Ser. No. 15/750,130 is very sensitive to the compressor's compression ratio. Very high compression ratios are required to reduce the inflation time of a bicycle tire. The high compression ratios require clearances smaller than 0.2 mm between the compressor's piston and the top of the compressor's cylinder when the piston is at top dead center, and such clearances can only be achieved using expensive CNC machining processes. This adds significant time and cost to manufacturing of the compressor parts, which is undesirable.
The Applicant's commercially successful miniFUMPA™, the subject of foreign patents, including U.S. Pat. No. 10,837,433, is a more portable pump than their FUMPA™ pump and so has, at least in part, addressed the portability issue of the FUMPA™ pump referred to above. The Applicant's miniFUMPA™ is the smallest electric pump currently available. However, it has a weight of around 200 grams, a pump length of around 75 mm, a height of around 70 mm (not including the nozzle) and a thickness 30-35 mm, making it too big to fit into a pocket, or a small handbag.
Thus, there is a need for a truly pocket-sized pump, having a weight of around 100 grams, a height of less than around 50 mm and a thickness around 25 mm. At this weight and dimensions, the pump could be taken on any bicycle journey in a user's pocket or in very small carry bag or handbag. Commuter cyclists would likely find such a pump appealing, as it could be placed in their bag or pocket on their way to work.
It would therefore be desirable to provide an air compressor arrangement of a very small size, and which can be incorporated into a battery-powered pump. Moreover, it would be desirable to provide a battery-powered pump design that is pocket sized, rechargeable, and can achieve fast pump up times that are less sensitive to the compressor's compression ratio. Finally, it would be desirable to provide a portable battery-powered bike pump that is dimensionally smaller than currently available bike pumps.
Finally, it would be desirable to provide an air compressor arrangement that at least partially addresses the issue of the compressor motor having to overcome an initially high start-up torque which can easily result in motor and/or circuit burnout; and which may desirably obviate the need for the given air compressor to require an unloader valve, which is a common air compressor failure point.
Before turning to a summary of the present invention, it is to be appreciated that the discussion of the background to the invention is included to explain the context of the invention. This is not to be taken as an addition that any of the material referred to is published, known or part of the common general knowledge.
The contents of the applicant's U.S. patent application Ser. No. 15/750,130 and U.S. Pat. No. 10,837,433 are herein incorporated by reference.
According to a broad aspect of the present invention, there is provided a reciprocating air compressor arrangement. The 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. The crank is 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 an outlet valve allowing compressed air to exit the cylinder. The inlet valve is biased to a partially open position and, during use, is movable between the partially open position, a closed position and a fully open position.
Reference to a ‘flapper valve’ in this specification is to be considered interchangeable with the term ‘reed valve’.
The outlet valve may be of any suitable one-way valve design. Like the inlet valve, the outlet may be a flapper valve. However, other outlet valve types are also contemplated, including a check valve.
Preferably, the cylinder includes a cylinder head, and the outlet valve includes an outlet port, with the outlet port extending through the cylinder head to allow for a flow of compressed air to exit the cylinder.
In one preferred form of the invention, the inlet valve includes an inlet port, with the inlet port extending through the cylinder head to allow for a flow of air to enter the cylinder.
In another preferred form of the invention, the piston includes a piston head, and the inlet valve includes an inlet port, with the inlet port extending through the piston head to allow for a flow of air to enter the cylinder.
It is envisaged that the air compressor arrangement is preferably 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.
The reciprocating air compressor arrangement of the present invention has a number of potentially useful applications, especially in the context of a portable pump. In this regard, and according to another broad aspect of the present invention, there is provided a portable pump including a reciprocating air compressor arrangement generally of the type referred to above. The 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. The crank is 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 includes a one-way flapper inlet valve allowing air to enter the cylinder, and an outlet valve allowing compressed air to exit the cylinder. The portable pump further includes 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. The portable pump further includes a control unit in electrical communication with the electric motor to control operation of the pump; and 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 are each contained within a common housing. An outlet is fluidly connected to the outlet valve of the reciprocating air compressor arrangement for fluidly engaging with an object to be pumped. The inlet valve is biased to a partially open position and, during use, is movable between the partially open position, a closed position and a fully open position.
The portable pump is preferably switchable between ON and OFF modes, with the inlet valve remaining in the partially open position when the portable pump is in the OFF mode.
In one preferred embodiment, the power supply of the portable pump 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.
The electric motor of the portable pump is preferably a brushless DC motor having a motor diameter of between approximately 20 and 30 mm and, more preferably, approximately 23 mm.
In a preferred form, the pump has a total weight of less than 100 grams, and can pump up at least one bicycle road or commuter bike tire to approximately 80 psi on a single charge.
The invention has the potential for incorporating a housing of very small dimensions when compared to the housings of existing portable pumps. In this regard, the housing may have 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.
In a preferred form, the pump outlet is provided on or mounted to the housing. The outlet may include a collar extending outwardly from the housing, with the collar including a valve receiving bore for receiving a valve of the object to be pumped.
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.
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.
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.
Where τ is the torque the motor can provide.
Reducing parameters such as cylinder diameter (and therefore piston diameter), or crank size (and therefore length Lc) 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.
One parameter that can be reduced is the length of the connecting rod 18, as shown in the prior art air compressor of
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.
It can be seen in
Reciprocating air compressors 210/310 of the type shown in
If an air compressor like the one shown in
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
One embodiment of the invention is now shown in
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.
The inlet valve 420 is, during use, movable between the partially open position shown in
The outlet valve 422 is movable between the closed positions shown in
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.
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
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.
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.
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
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.
The applicant has found that if a flat inlet valve (such as of the prior art types illustrated in
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.
The pump 400 includes a novel reciprocating air compressor arrangement generally of the type previously described.
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.
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.
Although not shown in
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.
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.
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.
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.
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021901420 | May 2021 | AU | national |
