Angle grinders are a hand tool commonly used in industry for, among other things, cutting and deburring metallic materials such as steel beams, rods and the like.. A typical angle grinder is comprised of an elongated motor housing, having a handle projecting perpendicularly out to the side near the front end of the housing. A drive shaft connects the motor to a grinding wheel located at the front of the tool, such that approximately one half of the wheel extends past the front of the motor housing. A wheel guard in the form of a half circle typically covers the distal half of the grinding wheel. The grinding wheel itself is formed as a thin disc, and is made of a hardened material. Other types of discs for various functions include a somewhat thicker disk for sanding, a so called"flap disc"for finer sanding/polishing, and a steel brush type disc.

In the case of the cutting operation, an operator uses the proximal edge of the rapidly-rotating wheel to cut through or deburr a work piece such as a piece of metal. As the wheel contacts the work piece, a hail of glowing sparks and debris is ejected from the edge of the wheel at extremely high velocity. These glowing sparks represent a fire hazard, and metal particles and other pieces of debris can be thrown long distances, creating a safety problem for other workers. The cutting operation and the operations performed using the other types of discs also create large amounts of gasses and dust, creating a serious health problem, especially in enclosed working conditions.

Heretofore there has been no effective device for capturing and removing the sparks, debris, gasses and dust from an angle grinder. While there have been efforts made to remove dust from other types of tools such as orbital sanders and grinders, the dust-removal devices associated with these tools would be ineffective for the currently-described problem.

A typical example of prior art dust-collection devices can be found in US patent 5,531, 639. This and similar devices generally describe dust-collection systems for sanding tools.

Such tools use the lower, flat surface of a rotating disc to abrade the surface of a work piece, such as a piece of wood.

Dust collects on the work piece in the vicinity of the tool, and turbulence from the rotating disc causes the dust to rise in to the air. Such dust-collection devices generally provide a means for creating a suction chamber or zone of negative pressure located directly above the disc. The disc is often perforated to allow the dust to be sucked up into this chamber or zone.

Because such tools use the surface of the sanding disc, rather than the edge as in the case of an angle grinder, particles are not ejected at high velocity. Therefore, a suction chamber located above the disc would be incapable of capturing particles ejected tangentially from the edge of a grinding wheel.

A further disadvantage of prior art devices is that known dust-removal apparatus are an integrated part of the tool itself. It would be financially unfeasible for companies to replace all of their existing angle grinders with ones incorporating an integrated dust-removal system. It would also be prohibitively expensive for manufacturers to redesign existing angle grinder models to incorporate an integrated dust-removal system such as that from US 5,531, 639.

A need exists, therefore, for a device that can capture and remove high velocity particles ejected from angle grinders and that can be retrofitted to virtually all existing models of angle grinders. It is important that such a device perform this function without interfering with the working edge of the grinding wheel.

The present invention overcomes the above-described problems by providing a curved collection shroud that may be attached to the wheel guard of virtually any standard angle grinder.

The collection shroud is attached using a bolt-and-spring arrangement that permits the shroud to move in several directions, thus preventing the shroud from interfering with the working edge of the grinding wheel. Sparks and particles ejected from the grinding wheel are captured by the shroud and led to an opening at the shroud's distal end. An internal rib leads the particles towards the opening, in which is mounted a miniature ejector. The ejector utilizes pressurized air to create a vacuum according to the venturi principle that removes the particles through a waste hose to a filter or other appropriate collection system. According to one aspect of the invention, the exhaust air from a pneumatic angle grinder is diverted to the ejector in order to create the vacuum. According to another aspect of the invention an external air supply is connected to the ejector, as in the case of an electric angle grinder.

The invention will be described in detail with reference to the following figures, wherein: Fig 1 is photograph of a workman using an angle grinder.

Fig 2 is a perspective view of the device according to the invention mounted on an electric angle grinder.

Fig 3 is the view from fig 1 shown from a different angle.

Fig 4 is an exploded view of figs 1 and 2.

Fig 5 is a perspective view of the collection shroud.

Fig 6 is a perspective view of the collection shroud, mounting bolts and springs and ejector arrangement.

Figs 7 and 8 are elevational cross section views of the collection shroud and ejector arrangement.

Fig 9 is a perspective cross sectional view of the collection shroud and ejector arrangement Fig 10 is an exploded cross sectional view of the collection shroud and ejector arrangement.

Fig 11 is a perspective view of the device according to the invention mounted on a pneumatic angle grinder.

Fig 12 is a perspective view of the compresses air diverter.

Fig 13 is a perspective view from fig 11 shown from a different angle.

Fig 14 is a perspective view of sparks being ejected from a grinding wheel.

Fig 15 is a perspective view of the sparks from fig 14 being captured by the device according to the invention.

The problem that the current invention attempts to solve is graphically represented in fig 1, which shows an industrial worker using an angle grinder to cut through a steel work piece. As can be seen in the figure, the cutting operation produces a shower of glowing sparks and debris thrown a great distance from the angle grinder. As can be appreciated, this represents a significant health and safety hazard.

Figs 1, 2 and 3 show the device according to one aspect of the invention mounted on an electrically powered angle grinder 20.

Angle grinder 20 generally comprises an elongated motor housing 22, a grinding wheel 24, the working edge of which extends past the proximal end of motor housing 22, and a semi- circular wheel guard 26 that covers the distal half of grinding wheel 24.

The device according to the invention comprises a curved collection shroud 28, the shape of which could generally be described as that of a concave scoop having an upper surface, a curved outer periphery and a lower surface. As seen in figs 5 and 6 the inner edge of said lower surface is significantly thinner than the inside edge of the upper surface, said lower surface being in fact tapered such that the inside edge of the lower surface is relatively sharp. This thinner edge prevents sparks from ricocheting off the edge.

Shroud 28 has two mounting holes 30 near the distal, inner edge of its upper surface as shown in fig 5. Said shroud 28 can be mounted to virtually any model angle grinder by using shroud 28 as a template to drill two corresponding mounting holes 30 in wheel guard 26 as shown in fig 4. As can be appreciated from fig 6, shroud 28 is flexibly mounted to wheel guard 26 by passing two mounting bolts 32 up through holes 30 in wheel guard 26 and collection shroud 28 respectively. Two springs 34 are placed axially over bolts 32, and tightened by two nuts 36. The diameter of holes 30 is preferably greater than the diameter of bolts 32 in order to permit shroud 28 to flex in relation to wheel guard 26 when pressure is applied to said shroud, for example when a worker presses the shroud against a work piece.

As can be seen in figs 2 and 3, the curvature of shroud 28 is designed such that a portion of grinding wheel 24 is inside the interior space defined by the upper and lower surfaces of shroud 28, and the length of shroud 28 is such that the proximal end of the shroud extends approximately the same distance from motor housing 22 as the proximal end of the grinding wheel. The shroud is therefore able to capture sparks and debris thrown from the grinding wheel, while at the same time not interfering with the working edge of the grinding wheel, as shown in figs 14 and 15.

Referring to figs 5 and 6 it can be seen that shroud 28 further comprises an internal rib 38, which angles back towards an exhaust sleeve 40, located at the distal end of shroud 28. A hole 42 extends through the upper surface of shroud 28 and into the interior of sleeve 40, as shown in fig 5. The proximal edge of exhaust sleeve 40 is rounded in order to reduce noise levels and to minimize turbulence.

As shown in figs 4,6, 7,8, 9 and 10, a miniature ejector is mounted concentrically in exhaust sleeve 40. The ejector comprises a cylindrical insert 44 having a conical distal end and a threaded cylindrical plug 46, having a concave proximal opening. The internal slope of the concave proximal opening of plug 46 is equal to the slope of the conical distal end of insert 44. The length of the body of plug 46 is designed such that, when insert 44 and plug 46 are aligned inside sleeve 40, the conical distal end of insert 44 is slightly concentric with the concave proximal end of plug 46 as shown in figs 7 and 8, thereby creating a ring shaped aperture 48. Said aperture 48 is thus angled in the direction away from the interior of shroud 28. In a preferred embodiment, the slope of the conical end of insert 44 and the concave proximal end of plug 46 is approximately 60 degrees, and the ring-shaped aperture 48, the size of which can be adjusted by screwing in or out plug 46, is between 0.5-1. 0 mm.

As shown in figs 4 and 7, an angled connector 50 is attached to hole 42. A first universal coupling 52 is attached to connector 50, and a second universal coupling 54 is attached to plug 46. A compressed air hose 56 is connected to universal coupling 52 and an exhaust hose 58 is connected to universal coupling 54. When compressed air is introduced through hose 56, a venturi effect is produced by the air passing through aperture 48. This effect produces a vacuum that draws air from the interior of collection shroud 28 into sleeve 40 and out through exhaust hose 58.

According to another aspect of the invention, as depicted in fig 11, the exhaust air from a pneumatically powered angle grinder 60 is diverted and utilized to power the ejector.

A typical pneumatic angle grinder comprises a motor powered by compressed air supplied by a compressed air hose 62. An operator depresses a handle 64 to admit the air flow that powers the tool. Exhaust air returning from the motor exits the distal of the grinder through a ring-shaped port (not shown), through the center of which passes air hose 62. In such grinders, an air-tight outer sheath (not shown) surrounds air hose 62. This sheath is coupled to the ring shaped port, such that exhaust air is led away in the medial space between air hose 62 and the sheath.

According to the present aspect of the invention, air hose 62 is uncoupled from the grinder and the sheath which normally is concentrically arranged around air hose 62 is removed. In place of the sheath, a cup shaped diverter member 66 is affixed to the distal end of the grinder. Air hose 62 is passed through a hole in the base of diverter member 66 and reconnected to the grinder. A small 0-ring 68 ensures an air tight seal between the air hose and the diverter member, while a large 0-ring 70 an air tight seal between the diverter member and the motor housing of the grinder. An exhaust port having a nipple 72 is located on the side wall of the diverter member. A connection hose 74 extends from nipple 72 to first universal coupling 52. Because the rate of air flow required to power the angle grinder is significantly greater than that needed to power the ejector, a relief valve 76 is located on the base of diverter member 66.

In use, the operator adjusts the position of wheel guard 26 such that the sparks ejected from the grinding wheel enter shroud 28. Centrifugal forces help lead the particles around the curvature of the shroud and back toward exhaust sleeve 40.

Because the ejector arrangement is located in the immediate vicinity of where the particles exit the shroud, less vacuum is required than would otherwise be necessary, thus reducing the noise level of the device. This vacuum is nonetheless sufficient to create a vacuum extending to the working edge of the grinding wheel that pulls away gasses and other particles not thrown directly into the shroud.

Because the device according to the invention is capable of being mounted to virtually any model of angle grinder, the invention can advantageously be provided as an accessory kit that can be easily assembled by the end-user.