Patent Description:
A compressor assembly typically includes a compressor mounted to a compressed air storage tank, an electric motor driving the compressor and an air discharge tube connected to the compressor and the air storage tank. The air storage tank provides a tank or receiver for storing a fluid, such as air, under pressure.

The compressor unit typically includes a piston assembly, or compressor pump, which compresses the fluid and forces it into the fluid pressure tank for temporary storage.

Likewise, an air compressor assembly provides a source of pressurized air to an air storage tank. Many portable air compressors include a compressor mounted to an air storage tank. The compressor compresses air which is then stored in the air storage tank. The compressor unit compresses air from the atmosphere. The pressurized air in the air storage tank can be used for operating air powered tools such as nailing tools, socket driving tools, material shaping tools, sanding tools, spray painting tools, inflation chucks, and inflating tires and the like.

Typically, the electric motor is an AC motor, requiring the air compressor assembly to be connected to an AC power source. However, a compressor with an AC motor cannot be used in places that do not have AC power or a nearby AC outlet.

Accordingly, some prior art solutions substitute the AC motor with a DC motor that can be powered from a battery pack. However, compressors typically have a (relatively) high energy demand. For example, a <NUM>. 4litre (<NUM> (four) gallon) compressor operating at in the range of <NUM> pascals (<NUM> psi) to <NUM> pascal (<NUM> psi (pounds per square inch)) may require in the range of <NUM>-<NUM> amps in order to compress the air sufficiently to operate a pneumatic device such as a pneumatic fastener, an impact wrench and the like. Therefore, the compressor must pressurize a sufficient quantity of air to at least a minimum operating pressure in order for the pneumatic device to operate properly. For instance, a brad nailer typically requires a much smaller quantity of air to drive a brad nail than is required for a framing nailer to drive a large nail such as a <NUM> d (sixteen penny nail). As a result, a pressure tank is typically included to store a sufficient quantity of air in order to meet a user's short term demand (e.g., a few shots of a pneumatic fastener in quick succession, a burst from an impact wrench sufficient to secure a lug nut), thereby allowing the compressor pump to "catch-up", or making no demand on the compressor pump. While the compressor usually is configured to handle a temporary demand of the type described above, the additional compressed air stored in a tank is usually surplus of air which may never be effectively utilized. In the foregoing situation, the compressor pump may expend a (relatively) large amount of energy in order to pressurize the air, in comparison to the energy expended to pressurize the air which is utilized to operate the pneumatically power device or attachment.

Therefore, it would be desirable to provide a compressor capable of utilization in environments lacking an electrical supply while providing a suitable airflow without the drawbacks previously experienced.

<CIT> discloses a cordless compressor having all of the features in the re-characterising portion of claim <NUM>.

<CIT> discloses a portable battery powered pneumatic fastening tool where a battery is used to power a compressor.

Accordingly, there is provided a cordless compressor in accordance with claim <NUM>.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:.

Referring generally to <FIG>, an air compressor assembly <NUM> in accordance with an exemplary embodiment of the present invention is described. The air compressor assembly <NUM> may be configured for utilization with a small demand fastener (a fastener requiring a small quantity of compressed air to operate) such as a finish nailer, or brad nailer. Persons skilled in the art are referred to <CIT>, entitled CORDLESS COMPRESSOR.

As shown in <FIG>, the air compressor assembly <NUM> includes a compressor <NUM> mounted to a compressed air storage tank <NUM>. Compressor <NUM> may include a pump <NUM> for generating a supply of compressed air. For instance, pump <NUM> may generate about <NUM> pascals (<NUM> psi (ninety pounds per square inch)) air supply with about <NUM>-<NUM> SCFM (cubic feet per minute at standard conditions) capacity. Pump <NUM> may have an inertia disk. Persons skilled in the art are referred to <CIT>, entitled "Cordless Compressor," for further information on the elements of compressor <NUM>.

Preferably pump <NUM> is selected so that it can have a maximum time from the time it is turned on (with a pressure of <NUM> pascal (<NUM> psi)) to the time it reaches a preset high pressure point, or "kick-out pressure," of about <NUM> pascal (<NUM> psi) in less than <NUM> seconds.

Air compressor assembly <NUM> includes a motor <NUM> coupled to the pump <NUM> for driving the pump <NUM>. Pump <NUM> is connected to the air storage tank <NUM>.

The air storage tank <NUM> provides a tank or receiver for storing a fluid, such as air, under pressure. Preferably the air storage tank <NUM> may be comprised of a flattened oval or "pancake" style tank of about <NUM> to <NUM> litres (<NUM>-<NUM> gallons s).

The air compressor assembly <NUM> is preferably sized to allow for hand transport by a single human of ordinary strength. To facilitate such transport, the air compressor assembly <NUM> may have a handle <NUM>. Handle <NUM> may be connected to a housing 10HH that at least partially encloses the motor and/or compressor <NUM>.

A roll cage <NUM> may be connected to the housing 10HH and surrounds air storage tank <NUM>. Preferably roll cage <NUM> protects portions of air storage tanks <NUM> from receiving impacts. Roll cage <NUM> may be directly attached to housing 10HH and/or tank <NUM>.

A discharge port <NUM> is connected to the air storage tank <NUM> to which a pressure manifold or pipe is fitted allowing compressed air to be drawn from the tank <NUM> for powering air powered tools such as nailing tools, socket driving tools, material shaping tools, sanding tools, spray painting tools, and tire inflation chucks.

A pressure switch assembly <NUM> inside of the compressor <NUM> is connected to motor <NUM> for regulating pressure within the air storage tank <NUM> by alternately starting and stopping the compressor <NUM> to periodically replenish the supply of air in the tank <NUM>. When pressure within the tank <NUM> reaches a preset low pressure point, or "kick-in pressure," the pressure switch assembly <NUM> starts the compressor <NUM> to re-pressurize the tank <NUM>. As the pressure within the tank <NUM> reaches a preset high pressure point, or "kick-out pressure," the pressure switch assembly <NUM> stops the compressor <NUM> to prevent over-pressurization of the tank <NUM>. In this manner, the pressure of the compressed air in the compressed air storage tank <NUM> is maintained within a range generally suitable for powering one or more air powered tools.

Persons skilled in the art shall recognize that pressure switch assembly <NUM> may be connected to controller circuit <NUM> (further described below), so that controller circuit <NUM> can receive the data from pressure switch assembly <NUM> and control the operation of motor <NUM> (and thus pump <NUM>).

A tank gauge <NUM> can show the pressure within tank <NUM>. A regulator <NUM> can be disposed between discharge port <NUM>, tank <NUM> and/or tank gauge <NUM> for controlling the output air pressure at discharge port <NUM>.

Persons skilled in the art will recognize that an output gauge (not shown) may be provided between regulator <NUM> and discharge port <NUM> to show the output air pressure. The need for such output gauge may be minimized if the regulator <NUM> is calibrated and indicia 17I are provided so that the user knows the expected air pressure from the position of the knob <NUM> of regulator <NUM>. Indicia 17I may be hot-stamped or embossed unto housing 10HH.

Preferably the knob <NUM> is rotatable less than <NUM> degrees throughout the entire pressure range, e.g. from <NUM> pascals (<NUM> psi) to <NUM> pascal (<NUM> psi), or from about <NUM> pascals (<NUM> psi) to about <NUM> pascals (<NUM> psi). Knob <NUM> may be threadingly engaged to a housing. The thread pitch is preferably between <NUM>-<NUM>.

Referring to <FIG>, an electrical system is preferably included in the air compressor assembly <NUM>. The electrical system includes a battery pack docking station <NUM> for receiving a battery pack <NUM>. Battery pack <NUM> is preferably a power tool battery pack having a nominal voltage of at least about <NUM>-<NUM> volts, and preferably about <NUM> volts. Persons skilled in the art are referred to <CIT> and <CIT>, for further reference on battery pack <NUM> and its connection to battery pack docking station <NUM>.

Persons skilled in the art shall recognize that different power tool battery packs <NUM> with different characteristics may be connectable to battery pack docking station <NUM>. For example, battery pack docking station <NUM> may receive (and compressor <NUM> may be operable) when a user connects a first power tool battery pack 107A that has a nominal voltage of at least about <NUM>-<NUM> volts. Similarly battery pack docking station <NUM> may also receive (and compressor <NUM> may be operable) when a user connects a second power tool battery pack 107B that has a nominal voltage of about <NUM> volts. Persons skilled in the art shall recognize that air compressor assembly <NUM> may have a step-down power converter to lower the nominal voltage of the second power tool battery pack 107B to a particular voltage, as disclosed in <CIT>.

First and second power tool battery packs 107A, 107B may also differ in other characteristics, such as battery cell chemistry, cell connection configuration, etc. For example, first power tool battery pack 107A may have a strand with a certain number of cells connected in series, while the second power tool battery pack 107B may have two strands of cells, each strand having the same number of cells connected in series, while both strands are connected in parallel in order to increase the overall capacity (measured in amp-hours) of the second power tool battery pack 107B. Alternatively, first and second power tool battery packs 107A, 107B may have different types of cells with different capacities, sizes, etc..

Second power tool battery pack 107B may also be a convertible battery pack where in a first configuration both strands are connected in series (increasing the overall voltage of the battery pack) while, in a second configuration, both strands are connected in parallel. Persons skilled in the art are referred to <CIT>, entitled "Convertible Battery Pack", for further information on alternate cell configurations and battery pack capabilities.

Compressor <NUM> has a controller circuit <NUM> for identifying the type of power tool battery pack <NUM> connected to battery pack docking station <NUM>. For example, first and second power tool battery packs 107A, 107B may have an identifying feature 107ID, such as an ID resistor, an ID capacitor, an ID number stored in a memory of battery pack <NUM>, etc. Persons skilled in the art are referred to <CIT> and <CIT>, for further information on possible configurations for such identifying features 107ID. Upon connecting power tool battery pack <NUM> to battery pack docking station <NUM>, controller circuit <NUM> would detect identifying feature 107ID (or query the battery pack <NUM>) to determine the type of battery pack and/or its characteristics, so that controller <NUM> can then control motor <NUM> in an advantageous manner, further described below.

Battery pack docking station <NUM> may be connected to a charger circuit <NUM>, which in turn is connected to an AC power source via power cord <NUM>. With such charger circuit <NUM>, battery pack <NUM> may be charged while connected to the battery pack docking station <NUM>.

Motor <NUM> preferably receives power from the battery pack <NUM> connected to the battery pack docking station <NUM>. Persons skilled in the art will recognize that motor <NUM> may also receive power from charger circuit <NUM> and/or power cord <NUM>, allowing a user to use air compressor assembly <NUM>, even if the battery pack <NUM> is fully discharged or not available.

Persons skilled in the art will recognize that air compressor assembly <NUM> may have multiple battery pack docking stations in the electrical system. In embodiments where multiple docking stations are utilized, the compressor electrical system may be constructed so as to draw electricity from battery packs <NUM> (received in the docking stations) in parallel, or concurrently such as when power is unavailable from a conventional power source (e.g. a commercially available alternating current source). In additional embodiments, a user operated switch may be included to allow the user to select from which battery/docking station power is to be drawn. Alternatively, an automatic switch may be included to switch from a first battery/docking station to second docking station based on a removable battery's available power, if a battery is coupled to the docking station, and the like.

Battery run-time may be extended by turning on pump <NUM> only when the pressure within the tank <NUM> reaches a preset low pressure point and turning off pump <NUM> when pressure within the tank <NUM> reaches a preset high pressure point, as well by selecting a pump <NUM> that does not draw too much current from the battery pack <NUM>. With the present arrangement, it is preferable to select a pump <NUM> that takes less than <NUM> seconds (and preferably around <NUM> seconds or less) to raise the pressure from tank <NUM> from a preset low pressure point of <NUM> pascals (<NUM> psi) to a preset high pressure point of <NUM> pascals (<NUM> psi).

By extending battery run-time, a larger number of nails may be driven by a nail gun powered by air compressor assembly <NUM>. For example, with the air compressor assembly <NUM> described in the present specification having a tank pressure of <NUM> pascals (135psi) can power an <NUM> gauge finish nailer to drive up to <NUM> nails on a single battery charge at a <NUM> pascals (<NUM> psi) setting.

The pressure switch assembly <NUM> is provided with multiple pressure switches that can be triggered at different air tank pressures. Controller circuit <NUM> would receive the information as to the status of the pressure switches, i.e., whether pressure switches are closed or opened. Because controller circuit <NUM> has recognized the type of power tool battery pack <NUM> connected to compressor <NUM>, it can control motor <NUM> in an advantageous manner as discussed below.

In an exemplary execution, pressure switch assembly <NUM> preferably has two mechanical pressure switches 13A, 13B, which close at <NUM> pascals (<NUM> PSI) and <NUM> pascals (<NUM> PSI), respectively. As described as one of the embodiments above, first power tool battery pack 107A has a single cell strand while the second power tool battery pack 107B has two cell strands connected in parallel. Accordingly, the first power tool battery pack 107A has a lower capacity (in amp-hours) than the second power tool battery pack 107B.

With such arrangement, controller circuit <NUM> can control motor <NUM> differently in response to the characteristics of the second power tool battery pack 107B. When the first power tool battery pack 107A is connected to compressor <NUM> and pressure within the tank <NUM> reaches a preset low pressure point, or "kick-in pressure," where both pressure switches 13A, 13B are closed, controller circuit <NUM> starts motor <NUM> to re-pressurize the tank <NUM>. As the pressure within the tank <NUM> reaches a particular pressure point, at least one of the pressure switches 13A, 13B will open. (Persons skilled in the art shall recognize that probably pressure switch 13A will open first, but to ensure that the logic algorithm carried out by controller circuit <NUM> does not result in an error, controller circuit <NUM> is programmed to stop motor <NUM> when either pressure switch 13A, 13B is open. ) Controller circuit <NUM> will not stop the motor <NUM> (and allow the tank pressure to continue rising) until both pressure switches 13A, 13B are open.

However, if controller circuit <NUM> detects that the higher capacity second power tool battery pack 107B is connected to compressor <NUM>, controller circuit <NUM> can control motor <NUM> differently. As before, when the second power tool battery pack 107B is connected to compressor <NUM> and pressure within the tank <NUM> reaches the preset low pressure point, or "kick-in pressure," where both pressure switches 13A, 13B are closed, controller circuit <NUM> starts motor <NUM> to re-pressurize the tank <NUM>. As the pressure within the tank <NUM> reaches a particular high pressure point, at least one of the pressure switches 13A, 13B will open. However, controller circuit <NUM> will not stop the motor <NUM> (and allow the tank pressure to continue rising) until both pressure switches 13A, 13B are open.

Persons skilled in the art shall recognize that, when both pressure switches 13A, 13B open, the tank pressure will be higher than when only one of the pressure switches open. This is advantageous as it allows compressor <NUM> to power the air powered tools for a longer time before having to repressurize tank <NUM>.

Controller circuit <NUM> may be programmed to follow a more complex logic. For example, controller circuit <NUM> may be programmed so that, at start-up, the controller circuit <NUM> may run motor <NUM> as long as one of pressure switches 13A, 13B is open, and stop when both pressure switches 13A, 13B are open when the second power tool battery pack 107B is connected to compressor <NUM>.

However, at states other than start-up, when only one of pressure switches 13A, 13B is open, the controller circuit <NUM> will continue the behaviour of the previous state. Accordingly, if motor <NUM> was running before one of the pressure switches 13A, 13B is open, the controller circuit <NUM> will continue to run motor <NUM>. On the other hand, if motor <NUM> was not running when one of the pressure switches 13A, 13B opened, the controller circuit <NUM> will not motor <NUM>.

Claim 1:
A cordless compressor comprising:
an air storage tank (<NUM>);
a pump (<NUM>) for pressuring air within the air storage tank (<NUM>);
a motor (<NUM>) for driving the pump (<NUM>);
a controller circuit (<NUM>) electrically connected to the motor (<NUM>);
a pressure switch assembly (<NUM>) connected to the controller circuit (<NUM>),;
a discharge port (<NUM>) connected to the air storage tank (<NUM>) ; and
a regulator (<NUM>) disposed between the discharge port (<NUM>) and the air storage tank (<NUM>);
a battery pack docking station (<NUM>) electrically connected to the motor (<NUM>), wherein a power tool battery pack (<NUM>) is electrically connectable to the battery pack docking station (<NUM>);
characterised in that the pressure switch assembly (<NUM>) has first and second pressure switches (13A, 13B) for sensing pressure within the air storage tank (<NUM>);
wherein the controller circuit (<NUM>) determines a characteristic and/or type of the power tool battery pack (<NUM>) electrically connected to the battery pack docking station (<NUM>);
wherein the controller circuit (<NUM>) controls de-activation of the motor (<NUM>) depending upon the status of the first and second pressure switches (13A, 13B) and the determined characteristic and/or type of the power tool battery pack (<NUM>).