Static electric discharge for dust collector

• US 5,150,499 A
• Filed: 11/16/1990
• Issued: 09/29/1992
• Est. Priority Date: 11/16/1990
• Status: Expired due to Term

• Current Assignee: Shop-Vac Corporation (Hangzhou Great Star Industrial Company Limited)
• Original Assignee: Shop-Vac Corporation (Hangzhou Great Star Industrial Company Limited)
• Inventors: Berfield, Robert C.
• Primary Examiner(s): Hornsby, Harvey C.
• Assistant Examiner(s): ALEXANDER, REGINALD
• Application Number:
  US07/614,711
• Time in Patent Office: 683 Days
• Field of Search: 15/339, 15/377, 15/327.1, 15/327.7, 174/47, 361/212, 361/215, 361/220, 361/221, 361/222, 285/7
• US Class Current: 15/327.1
• CPC Class Codes: A47L 9/24 Hoses or pipes; Hose or pipe couplings hoses or hose joints in general F16L
• CPC Class Codes: A47L 9/2889 Safety or protection devices or systems, e.g. for prevention of motor over-heating or for protection of the user
• CPC Class Codes: H05F 3/02 by means of earthing connections

Abstract

An anti-static dust collector includes a tank and an electrically non-conductive flexible hose, both of which are susceptible to the build-up of static electric charge. To remove such charge from the hose, the hose includes a helical wire which is connected to the grounding terminal of the electrical power plug used to supply electric power to the dust collector. Where the housing of the vacuum cleaner is electrically non-conductive, accumulation of electrostatic charge from the housing is removed by a metallic strap connected to the interior of the housing and also electrically connected to the grounding terminal of the power plug.

Claims

1. A dust collector comprising:

a dust collecting tank having an internal chamber, an open top and an air inlet duct into the tank chamber;

a separable lid attached to the tank over the open top;

suction means, supported on the lid, responsive to electrical power for generating reduced air pressure within the chamber;

first electrical connecting means, including a grounding element, for connecting the suction means to a source of electric power including a source of ground potential;

an electrically non-conductive hose having an outlet end connecting to the air inlet duct and having an inlet end through which air may be drawn into the hose when reduced air pressure is generated within the chamber;

an electrically conductive element extending along and contacting the hose and providing a low resistance path to any electrostatic charge which may develop on the hose; and

second electrical connecting means for connecting the electrically conductive element to the ground element of the first electrical connecting means, the second electrical connecting means comprising a tank contact on the tank electrically connectable with the electrically conductive element, the tank contact including a first metallic strap at the inlet duct to the tank and a lid contact on the lip connected with the grounding element, and arranged for engaging the first metallic strap regardless of the orientation of the lid when the lid is on the tank to thereby assure electrical contact between the tank contact and the ground element.

2. The dust collector of claim 1, wherein the conductive element is inside and in contact with the interior of the hose along the length of the conductive element.

3. The dust collector of claim 1, in which the first conductive element is a flexible helical electrical wire in contact with the hose along the length of the wire and of the hose.

4. The dust collector of claim 3, wherein the wire is insulated.

5. The dust collector of claim 1, in which the tank inlet duct is comprised of an electrically non-conductive material, the second electric connecting means includes a first metallic strap at the inlet duct to the tank;

the helical wire is electrically connectable to the first strap.

6. The dust collector of claim 5, in which the tank is also of non-conductive material, and a second conductive strap extends along the tank to provide a low resistance path for any electrostatic charges which may build up on the tank, and the second strap is connected to the connecting means.

7. The dust collector of claim 1, wherein the inlet duct is formed in the tank.

8. The dust collector of claim 1, in which the tank has an upper rim which defines the open top, the lid has a lower rim mateable with the upper rim of the tank for sealing the lid to the tank.

9. The dust collector of claim 8, wherein the tank contact is on the upper rim and the lid contact is on the lower rim.

10. The dust collector of claim 1, in which the tank inlet duct is comprised of an electrically non-conductive material, the second electrical connecting means includes a first metallic strap at the inlet duct to the tank;

the conductive element includes a helical wire electrically connectable to the first strap; and

the first metallic strap includes the tank contact on it.

11. A dust collector comprising:

a dust collecting tank having an internal chamber, an open top and an air inlet duct into the tank chamber, the tank inlet duct being comprised of an electrically non-conductive material;

a separable lid attached to the tank over the open top;

suction means, supported on the lid, responsive to electrical power for generating reduced air pressure within the chamber;

first electrical connecting means, including a grounding element, for connecting the suction means to a source of electric power including a source of ground potential;

an electrically non-conductive hose having an outlet end connecting to the air inlet duct and having an inlet end through which air may be drawn into the hose when reduced air pressure is generated within the chamber;

an electrical conductive element in the form of a helical wire extending along and contacting the hose and providing a low resistance path to any electrostatic charge which may develop to the hose; and

second electrical connecting means for connecting the electrically conductive element to the ground element of the first electrical connecting means, the second electrical connecting means comprising (a) a tank contact on the tank electrically connectable with the electrically conductive element, the tank contact including a first metallic strap at the inlet duct to the tank, the first metallic strap being connectable to the helical wire of the electrically conductive element and (b) a lid contact on the lid connected with the grounding element, the lid contact including a circular metallic ring connected to the lower rim of the lid and placed for engaging the first metallic strap regardless of the orientation of the lid when the lid is on the tank to thereby complete electrical contact between the tank contact and the lid contact.

12. The dust collector of claim 11, wherein the inlet duct is formed in the tank.

13. The dust collector of claim 11, in which the tank is also of non-conductive material, and a second conductive strap extends along the tank to provide a low resistance path for any electrostatic charges which may build up on the tank, and the second strap is connected to the tank contact.

14. The dust collector of claim 13, wherein the second conductive strap is in the chamber.

15. The dust collector of claim 13, wherein the tank contact for the first and second conductive straps is the same.

16. The dust collector of claim 11, in which the suction means includes a motor and a suction fan driven by the motor;

the electrical connecting means includes a three-prong plug, one of the prongs being adapted to be inserted into a ground receptacle; and

the lid contact is electrically connected to the grounding prong.

17. The dust collector of claim 16, in which the lid includes a filter support element in communication with the chamber and with the suction means;

and in which the lid further includes an outlet duct from the suction means, and the outlet duct is adapted to receive a dust collection bag.