Air pump apparatus

Abstract: Portable, low noise air pump apparatus employing an inexpensive lightweight pump and motor unit (13), which pumps a pulsed noisy output into a plenum chamber (14) inside a rubber impervious sub-housing (64) which absorbs noise and vibration; and a sound deadening plastics tube (31) which carries the compressed air from the plenum, via a sound absorbing chamber (66) (surrounded by lightweight sound absorbing material (30) which supports the sub-housing) and across an accommodation space (62) to an outlet fitting (25) from which a smooth low-noise compressed air output can be supplied.

Description: This invention concerns air pump apparatus, which is generally of a kind comprising:- (a) a rigid housing (b) a sound absorption chamber in said housing (c) a pump in said sound absorption chamber (d) a duct within said housing for conveying pumped air to an outlet. In US-A-4950133 there is disclosed an air blower assembly which is generally of said kind, but in which the pump is in the form of a blower which operates at high speed to provide a flow of air for aerating a spa tub. The blower produces a high pitched whine, and to reduce this whine, the sound absorption chamber is in the form of an air inlet chamber in which the blower is mounted (in a nest of acoustical foam at one side of an internal platform at one end of the air inlet chamber) to blow air from the air inlet chamber, past the motor, into the duct which is in the form of a central outlet passage which is separated from the air inlet chamber by the internal platform. There are other goods of said kind (e.g. motor tyre inflators and air compressors for vehicle horns) in which the pumps are noisy producers of compressed air, but for which the sales market for such goods is so large and the operational requirements so simple that the cost thereof can be minimised by volume mass production. However, such pumps are inherently noisy and are not suitable for other purposes where noise is detrimental. Additionally, there are requirements for relatively small quantities of pump units for special applications requiring complex control systems, such as pump units for air pump apparatus for powering and controlling pneumatically operated equipment, e.g. lifting seats for disabled persons or dentists drills, but such specialised pump units are invariably relatively expensive, complex and massive, and are of a kind which has a heavy housing which provides some sound absorption. These problems of pump noise, expense, complexity and bulk are faced by the invention, and to reduce these problems in apparatus of said kind the apparatus is characterised in that:- (e) said apparatus further comprises a sub-housing which is disposed inside the sound absorption chamber and defines a sealed plenum chamber within the sound absorption chamber; (f) said pump is incorporated in a pump and motor unit in said sealed plenum chamber to discharge air under pressure into said plenum chamber, and (g) said duct is connected in the sound absorption chamber to said sub-housing to convey air under pressure from the sealed plenum chamber. Preferably, the pump and motor unit is located in the plenum chamber by a mounting of vibration damping material. A flow control valve or valves may be disposed in the plenum chamber and/or in the sound absorption chamber. The sound absorption chamber is preferably surrounded by sound absorbent material which defines that chamber within the housing. The arrangement of the chambers is preferably such that the air, passed through the apparatus, is constrained to flow sequentially through the chambers, preferably along a reflex path. The pump and motor unit preferably has a casing provided with an air inlet and air outlet. The air inlet is preferably connected to an inlet duct which extends through the sub-housing to the sound absorption chamber. A reverse air-flow path is preferably provided from the plenum chamber to the sound absorption chamber. The valves preferably include an electrically actuable valve located in the sound absorption chamber. A filter is preferably included in an air flow path between the sound absorption chamber and an accommodation space in the housing. The sound absorbent material may constitute the filter or part of the filter. The apparatus may include a battery, preferably located in the accommodation space. The housing preferably comprises an elongate length of rigid tube having end closures. A pipe connection fitting, for pumped air, and manually actuable control means or connection means to connect with manually actuable control means are preferably provided on or exposed via one of the end closures. The tube is preferably a plastics extrusion. The apparatus may form one of a range thereof differing in some respects, such as in length, internal arrangement, or end closure configuration, but otherwise of similar general structure in which many common components are employed. Electrical operating means preferably comprises circuitry mounted on a circuit board located in the accommodation space, through which space there passes a pipe connecting the plenum chamber directly or indirectly with the pipe connection fitting. The apparatus is preferably arranged so that an inlet flow path for inlet air is provided within the housing between a vent in said end closure and the pump, so that said circuit board and valve are passed by air flowing along the inlet flow path to the inlet duct. A battery is preferably located in the accommodation space on a carrier which preferably also supports the circuit board, pipe connection fitting, control means or electrical connection means for a remote control handset, and which carrier may be provided with electrical input terminals for re-charging the battery. The apparatus may be arranged to deliver air under pressure to the pipe connection fitting, or to deliver air under pressure to and withdraw air under suction from the pipe connection fitting. The valve is preferably actuable to allow air under pressure at the pipe connection fitting to vent back to atmosphere along the reverse flow path via the plenum chamber, the sound absorption chamber, the accommodation space and the air vent. The electrical operating means is preferably arranged to open the valve when the pump is running, to close the valve when the pump is not running and to control the opening and closing of the valve when the pump is not running to selectively prevent or permit air to flow through the plenum chamber or a sound absorption chamber. The user of pump apparatus faces problems with the storage of fittings for the apparatus, which problems can be severe in the case of pump apparatus for powering aids for disabled users. To reduce such problems, the housing preferably supports a cover assembly, which cover assembly includes an openable storage compartment for storing fittings and accessories for the apparatus. The housing may be cylindrical, and the storage compartment is preferably arranged to support the housing against being rolled. The invention includes pneumatic support or lifting apparatus such as a wheelchair comprising a pneumatically operated device coupled to or incorporating air pump apparatus of the invention. The apparatus of the invention can thus utilise a lightweight and inexpensive air compressor unit of the kind produced for vehicle horns, to be employed as the pump and motor of the apparatus in situations in which the noise produced by such an air compressor unit would otherwise be unacceptable. The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein:- FIGURES 1 and 2 are schematic cut-away drawings showing the general arrangement of a first and second embodiments of air pump apparatus of the invention; FIGURE 3 shows a front end view of the apparatus with a diagrammatic representation of a lifting device in a wheelchair, and a remote control unit; FIGURES 4, 4A and 4B are circuit diagrams for the operating and control means incorporated in the first embodiment; and FIGURES 5 and 5A show circuit diagrams for the operating and control means of the second embodiment. Referring to FIGURES 1 and 2, each of the embodiments of the pump apparatus primarily comprises a housing 11 containing a battery 12, a pump and motor unit 13, a plenum chamber 14, a solenoid actuated normally closed valve 15 and/or 15A or 15B and a circuit board 16. The housing includes a rigid cylindrical body 17, a rear end closure 18 and a front end closure 19. The body 17 is a length of inexpensive mass produced circular cross-section extruded plastics tubing. Each end closure is a moulded plastics cover, the front cover being modified to expose certain parts and fittings of the apparatus which are mounted on a battery support frame 60. The parts include a holder 20 for a motor fuse 40, a holder 21 for a control circuit fuse 41, a charge input socket connector 22, a pumped air connection fitting 25 for reception of a connector 10D of a pressure supply line 10E to a pneumatically actuated lifting device 10F of an aid for a disabled person, for example, a wheelchair 10G, and an electrical socket connector 61 for reception of a plug lead connector 10A to a remote control handset 10B incorporating a combined centre-off control switch 10C incorporating an up-switch 23 and a down-switch 24 shown in FIGURES 3 and 4 to 5. A duplicate switch 10C may be provided at the front cover as indicated in broken lines in FIGURE 3. Two air inlet vents 26 are also provided in the closure 19, which is releasably secured to the frame 60. The frame 60 is secured to the body 17 of the housing 11 in an accommodation space 62 in the housing. The battery 12 is a sealed rechargeable 12 volt battery, having terminals 27 and 28, and is secured in the frame 60. The unit 13 is an inexpensive light, but noisy, mass produced 12 volt air compressor (of a kind intended for vehicle air-horns) which comprises a pump 13A and a motor 13B housed in a casing 63 having an air inlet 33A and an air outlet. The front end portion of the unit 13, i.e. that portion of the unit 13 in which the pump is disposed, is embedded in a mounting comprising body 29 of an impervious, e.g. solid, vibration absorbing material, such as rubber, visco-elastic or elastomeric material, which is set in the front end portion of a thick walled sub-housing 64 of similar vibration damping or absorbent material such as plastics or rubber material so that the unit 13 extends in cantilever manner along the chamber 14. The remainder of the interior of the sub-housing constitutes the plenum chamber 14 and a rear portion of the sub-housing 64 is provided by a sealing closure 65. The sub-housing 64 and the valve 15 and/or 15A or 15B is or are located in a sound absorbing chamber 66 defined by or substantially filled with sound absorption material 30, such as plastics sheet backed porous foamed plastics or elastomeric material or a fibrous material, which material 30 supports at least portions of the valve and housing 64. A pumped-air tube 31 extends within the chamber 66, is secured to the closure 65 and connects the plenum chamber 14 directly or indirectly with a tube 35 to the pumped or working air connection fitting 25. The air inlet 33A of the unit 13 is connected to an air inlet supply pipe 33, which pipe is made from flexible preferably vibration absorbent material, and the pipe 33 passes through the plenum chamber 14 and the sub-housing 64 to the sound absorption chamber 66 in which the valve 15 and/or 15A is located. An air pressure line 36 connects the tube 35 (or possibly the fitting 25 or the chamber 14) with a pressure sensitive limit switch 37 on the circuit board 16. The apparatus is provided with a cover assembly 70 comprising a cylindrical fabric cover 71, which surrounds and grips or is adhered to the peripheral surface of body 17 of the housing between peripheral flanges 34 on the closures 18 and 19, and a storage compartment 72 having a flat bottom 73 tangential to the housing. The compartment 72 has a lid 74. A handle 75 is provided at the top of the assembly 70. The handle may be secured to the cover 71 or the body 17. Apertures in the front closure 19 give access to the fittings mounted on the battery support frame 60: removal of the closure by releasing fasteners 76 gives access to the battery. The circuit board 16 carries circuitry and electrical components of electrical operating means which is actuable by manually actuable control means which comprises the remote control unit or handset 10B incorporating the up and down switches which is connectable via a cable having the plug connector 10A insertable into the socket connector 61. The first and second embodiments of the apparatus differ in that the first embodiment (FIGURES 1 and 4,A,B) is controllable to pump air to and suck air from the fitting 25, whereas the second embodiment (FIGURES 2 and 5,A) is arranged only to pump air to the fitting 25. Depending upon the embodiment, the operating and control means may provide for bi-directional operation of the unit 13 employing a circuit such as is shown in FIGURE 4,4A,4B or for unidirectional operation of the unit employing a circuit such as is shown in FIGURE 5,5A. In the first embodiment shown in FIGURE 1, the valve 15 is interposed between the tubes 31 and 35 and, as shown in FIGURE 4, the circuit includes a "down" relay 42 controlled by the switch 24, a safety relay 43 controlled by the pressure switch 37 and an up relay 44 controlled by the switch 23. In the off condition of the circuit (which condition is illustrated in all FIGURES) the motor 45 of the unit 13 and the valve 15 are de-energised. The battery can be trickle charged via the connector 22 and fuse 41. When the up switch 23 is closed, the up relay 44 and the valve 15 are energised to energise the motor 45 and open the valve 15 to cause air to be pumped under pressure into the chamber 14, to traverse said chamber 14 and enter the pipe 31 in which it flows forwards within the chamber 66 and via the valve 15 and pipe 35 to the fitting 25; and to draw relief air into the housing via the inlet vents 26 to flow past the circuit board and valve, to enter the front end of the chamber 66 and flow rearwards to the rear end, and to flow into the pipe 33 at said rear end and along said pipe forwards across the chamber 14 to an air inlet 33A of the unit 13. If the pressure limit set by the switch 37 is reached, this switch closes to energise relay 43 which de-energises the relay 44 shutting off the motor, and removes the power supply to the valve 15 so that the valve closes. When the down switch 24 is closed, relay 42 is energised to energise and open the valve 15 without energising the motor and irrespective of the condition of the switch 37, so that air under pressure can flow back from the fitting 25 to the vent 26 via the unit 13. For operating the unit 13 reversibly, the circuit includes pole-reversing relays 50 and 51 and an exhaust switch 53, which switch or a duplicate thereof can also be provided in the remote control unit and/or at the cover 19. Switch 53 is fed via switch 24 so that when both switches 24 and 53 are closed relays 50 and 51 are energised to energise the motor 45 with reversed polarity of the electrical supply at the same time as the valve 15 is opened, thereby pumping air from fitting 25 to vents 26 via the chamber 14. It will be readily appreciated that in the first embodiment when only the switch 24 is closed, air under pressure at the fitting 25 can flow back via the unit 13 in which the undriven pump serves as an impedance. If rapid but unpumped venting of air under pressure at the fitting 25 is required in the first embodiment, an additional valve 15A (indicated in broken line in FIGURE 1) can be connected to the plenum chamber by a further tube 38, and a vent selection switch 53 included in the control circuit as shown in FIGURE 4A. In the second embodiment, the valve 15 is omitted and the outlet from the unit 13 passes through a mechanical non-return valve 67 and through a normally open path through (FIGURE 5A) or by-passing (FIGURE 5) the valve 15B to the pipe 35; and the valve 15B is not connected to the plenum chamber by a further tube 38 mounted on the closure 65, but instead opens, when energised, a branch port 15C to discharge air from the pipe 35 directly into the chamber 66 so as to be silenced with minimum flow restriction. The control circuit is simplified as shown in FIGURES 5 and 5A so that the motor is unidirectionally energisable via switch 23 and normal closed relay 43, and can be isolated by energisation of relay 43 by pressure switch 37. The port 15C of the valve 15B remains closed during pumping, and at other times unless switch 24 is closed to allow air under pressure at the fitting 25 to flow back via the tube 35, the valve 15B, the chamber 66 and the accommodation space 62 to the vents 26. The valve 15B could be inserted into the tube 31 or 35 in the first embodiment as a substitute for the valve 15A and tube 38. Both circuits may be adapted for direct instead of or as well as remote actuation. For example, the switches 23 and 24, or 23, 24 and 53 may be located on the front cover 19 instead of in a portable hand-held control unit, or, as shown in broken lines in FIGURES 5 and 5A supplementary switches e.g. 23B and 24B may be mounted on the cover 19 e.g. as a combined "centre-off" switch assembly 10C, to enable the apparatus to be operated when the remote control unit is disconnected from the socket 61. Both circuits are easily adapted for rapid recharging of the battery, and/or direct operation with or without a battery, by modification of the circuits as shown in FIGURE 4B. As can be seen from FIGURES 1 and 2, the sub-housing 64 is relatively thick walled and is made from a solid or otherwise impervious vibration absorbing elastomeric or plastics material; and the sound absorption chamber 66 is filled partially with porous packing e.g. the layer 69 which serves to support the tubes and the sub-housing 64 as well as to absorb some of the noise from the unit 13. Further porous or fibrous material 69A may be located in the voids shown around the valve 15 and tubes to substantially fill the chamber 66 as indicated in FIGURE 2. The annular front end portion 80 of the peripheral layer of sound absorbent material 30 serves as an annular air inlet to the chamber 66 around the front face 81 of the foremost sheet plastics layer of the sound absorbent material 30, so that the peripheral layer serves as an air filter. Further noise/vibration absorption may be provided by the layer 69 and any additional fibrous material in the chamber 66. The arrangement of the chambers, sound absorbing materials and filtration of the air flows provides a smooth flow of pumped air quietly from a noisy and pulsed output from the unit 13. The noise reduction is further improved by the use of flexible materials which are poor transmitters of sound for the tubes 31, 33, 35 and 38. The valve 15, 15A or valves 15 and 15A may be located in the chamber 14, but if the valve 15B is located in the chamber 14, the port 15C will have to be fitted with a tube to convey air out of the chamber 14 e.g. to the chamber 66. The air pump apparatus enables an air pressure operated device to be solely operated by air which is passed through a single line between said device and the pump unit of the pump apparatus so that all air flowing in said line to and from said device under the control of the valve means of the apparatus is constrained to flow through the sound absorbing chamber within the apparatus.

Claims: Air pump apparatus comprising:- (a) a rigid housing (17) (b) a sound absorption chamber (66) in said housing (c) a pump (13A) in said sound absorption chamber (66) (d) ducts (31,35) within said housing for conveying pumped air to an outlet (25) and characterised in that:- (e) said apparatus further comprises a sub-housing (64) which is disposed inside the sound absorption chamber and defines a sealed plenum chamber (14) within the sound absorption chamber (66) (f) said pump (13A) is incorporated in a pump and motor unit (13) in said sealed plenum chamber (14) to discharge air under pressure into said plenum chamber, and (g) said duct (31) is connected in the sound absorption chamber to said sub-housing to convey air under pressure from the sealed plenum chamber. Apparatus as claimed in Claim 1 further including sound absorbing material (30:30,69A) which defines or fills the sound absorption chamber (66). Apparatus as claimed in Claim 2 and further characterised in that the pump (13A) is arranged to draw air through the sound absorbing material (30). Apparatus as claimed in Claim 3 wherein the material (30) is porous and constitutes filter means for air flowing to the pump. Apparatus as claimed in Claim 2, 3 or 4 further characterised in that the sub-housing (64) is mechanically supported by said sound absorbing material (30), and is made of an impervious polymeric material. Apparatus as claimed in Claim 2, 3, 4 or 5 wherein a valve or valves (15,15A,15B;67) is or are located within the sound absorption chamber by the sound absorbent material. Apparatus as claimed in Claim 6 wherein a supply duct (33) extends to the pump and motor unit (13), and further characterised in that said duct (33) extends through the plenum chamber (14) from the sound absorption chamber (66). Apparatus as claimed in Claim 7 wherein the arrangement of the chambers (14 and 66) and ducts (31,33 and 35) is such that the air, passed through the apparatus, is constrained to flow sequentially through:- (a) the sound absorption chamber; (b) the supply duct in the plenum chamber; (c) the pump; (d) the plenum chamber; (e) the duct within the sound absorption chamber, and (f) the valve; so as to enter and leave via one end of the sound absorption chamber, the ducts being of a flexible pipe or tube material which is a poor transmitter of sound. Apparatus as claimed in Claim 6, 7 or 8 wherein the valve or valves are electrically actuated. Apparatus as claimed in Claim 9 wherein the housing (11) comprises an elongate body (17) having end closures (18,19); wherein a pipe connection outlet fitting (25), for pumped air, and electrical connection means (22,61) are located at one of the end closures (19); wherein electrical operating means, comprising circuitry mounted on a circuit board (16), is located in an accommodation space (62) in the housing, through which space there passes the duct (35) connecting the pipe connection fitting (25) with the valve (15,15A,15B); and wherein the apparatus is arranged so that an inlet flow path for inlet air is provided within the housing between a vent (26) in said end closure (19) and the pump, so that said circuit board and valve are passed by air flowing along the inlet flow path to the pump and motor unit (13). Apparatus as claimed in Claim 10 wherein a battery (12) is located in the accommodation space (62) on a carrier (60) which also supports the circuit board (16), the pipe connection fitting (25), a control switch (10C) and/or an electrical connector (61) for receiving a connector (10A) of a lead to a remote handset (10B), and which carrier is provided with electrical input terminals (22) for recharging the battery (12). Apparatus as claimed in any preceding claim wherein the housing (11) is rigid and directly supports a cover assembly (70), which cover assembly includes an openable storage compartment (72) for storing fittings and accessories for the apparatus; and wherein the housing is cylindrical, and the storage compartment is arranged to support the housing against being rolled. Pneumatic support or lifting apparatus comprising the air pump apparatus as claimed in any preceding claim and a pneumatically operable device (10G) coupled to said air pump apparatus. Pneumatic apparatus as claimed in Claim 13 as appended to Claim 6 wherein the pneumatic apparatus includes an air pressure operated device (10F) which is operated by air which is passed through a single line (10E) between said device and the air pump apparatus so that all air flowing in said line (10E) to and from said device under the control of the valve or the valves of the apparatus is constrained to flow through the sound absorbing chamber.

Inventors: FLETCHER RICHARD EDMOND, RIMINGTON RICHARD MICHAEL, FLETCHER, RICHARD EDMOND, RIMINGTON, RICHARD MICHAEL
Applicants: MANGAR INTERNATIONAL LTD, MANGAR INTERNATIONAL LIMITED
Application year: 1993
Main classification: F04D29
IPC codes: F04C29, F04D29