The invention concerns a portable grinding machine with casing which is equipped with a rotor operated grinding tool on its front and a top handle on its back as well as a speed control mechanism with which the rotation speed can be regulated via a speed setting feature.
Grinding machines are used to remove coatings, lacquer and paint from surfaces of a variety of objects and are known for example from the EP 0 577 575 or the DE-PS 39 33 885. A possible area of use for these grinding machines is the removal of paint from the exterior surfaces of vehicles where it is necessary to follow the uneven lines of such a vehicle. For this, portable machines are being used which the user can hold with one hand and set onto the surface. The speed regulation needs to be adjusted multiple times for various tasks on one object depending on whether the full surface is being worked on or if edges or hollow moldings are involved. This is accomplished by a speed control mechanism, which is operated with the other hand. In order to change the speed the machine usually has to be taken off the surface because the pressure of the grinding tool onto the surface cannot be kept constant during the regulation of the speed which then could cause damage to the surface. On many known grinding machines the switch for the speed regulation is located below the flat of the hand. Another disadvantage of most common machines is that top handles in different sizes have to be used which need to be exchanged depending on the size of the hand of the user. This is especially true for use of the same piece of equipment by left or right-handed users and different hand sizes between men and women. These four different requirements by potential users can be addressed by making the top handles exchangeable so that each user can pick a top handle that is fitted more or less suitable for him or her. However, this involves extra cost, time and effort since the machine needs to be equipped with a different top handle, which then also needs to be securely and appropriately held in place.
The task of the submitted invention is to develop a portable grinding machine for which the speed can be adjusted easily without lifting the equipment off the surface of the object and which can be operated by various users without extensive conversions.
The task of the invention is solved by enabling the speed-setting feature to swivel around an axis perpendicular to the grinding machine and placing it at the upper edge of the top handle. This enables the user to operate the equipment with one hand. The inside of the hand or the palm is placed on the top handle on the back of the equipment while the fingers, especially the index or the middle finger can operate the speed setting feature. The speed setting feature is able to swivel around an axis essentially vertical to the grinding machine thus the same direction of the axis upon which the user applies pressure on the grinding machine. During the grinding process, the speed can continuously be changed and therefore adjusted to the objective of the work depending on whether the grinding machine is used with its complete grinding surface, partial surface or with its edge. An especially even and safe operation is made possible because only one hand applies pressure onto the equipment and the surface of the work object while setting the speed. Sudden, jerky motions during the application of the grinding machine onto the surface, which were inevitable when the speed was regulated by the other hand, can therefore be avoided.
The grinding machine can be operated especially well, if the speed setting feature is positioned so that holding the top handle and operating the speed setting feature with only one hand is possible and that the speed setting feature is within reach of the index or middle finger. For this reason, the speed-setting feature is placed directly below the covering of the top handle at the upper edge of the top handle so that this feature can be reached easily. At the same time, the distance in radial direction has to allow for an easily operation for the index- and middle finger. Therefore, it is assumed that the axis of the grinding machine and the top handle are the same.
The speed setting feature is placed on the outside of the casing and corresponds with an interior speed control mechanism. To connect the parts, the speed setting feature is directly connected to the speed control mechanism via a regulator ring which is located on the inside of the top handle and is mounted on a pivot. The axis of the regulator ring corresponds with the axis of the grinding machine and the top handle. The operation of the speed-setting feature moves the regulator ring around this axis and translates this motion onto the cylindrical speed control mechanism.
The regulator ring is equipped with a covering below which the speed setting feature juts out slightly, or better, the speed setting feature is placed above its radial limits jutting out slightly. It is understood, that the radial limit of the covering is at least almost identical to the radius of the motion of the speed-setting feature.
The invented grinding machine can be powered by pressure or electricity. Functionally, a pneumatic drive is envisioned which is equipped with a supply connection as well as a vitiated air connection while the supply connection correlates to an air intake valve into the rotor area. This air intake valve, detailed in the following text, is operated by a feature which can also be operated by the same hand.
An on/off switch located at the top handle, moveable towards the top handle and slightly jutting out will be the main device to operate the machine. This piece of the equipment is fit the form of the top handle so that it can also be operated by the back of the hand. To turn the machine on, the piece is pushed towards the top handle, or more precisely the grinding machine, against the pressure of a spring or turned around an appropriate joint. If the back of the hand is lifted slightly, the same part is pushed back into its off-position due to the pressure of the spring and moves away from the top handle, so that the machine will be turned off instantly due to the interruption of the pressure supply.
The operating device and the supply connection or air intake valve are connected through a valve pestle in the operating device, which correlates to the speed control mechanism. The side of the valve pestle, which faces away from the operating device has a connection to the air intake valve. By moving the operating device towards the top handle, the valve pestle is pushed along its longitudinal axis so that the air intake bores are opened and pressurized air can flow into the rotor area. If the operating device is moved in opposite direction, the valve pestle closes the air intake bores and the air supply will be shut off. By moving the pestle, the machine can be quickly turned on and off and by turning the speed control mechanism which surrounds the pestle the rotation speed of the grinding machine can be regulated for all settings between zero and maxim power.
To regulate the speed of the grinding tool, it is suggested that the speed control mechanism has at least one, preferably two drill-holes at its end pointing towards the air intake valve. These drill-holes correlate to a air intake bore in the air intake valve. By turning the speed setting control and therefore the speed control mechanism, the drill-holes at end of the speed control mechanism will be brought into position with the air intake bores.
A preferred version of the invention intends that the drill-holes and the air intake bores are built and set to cover each other partially or completely depending on the position of the speed control mechanism. Air flows via the supply connection or the air intake valve and the drill-holes into the rotor room, depending on how far one of these drill-holes overlap with the air intake valve. The revolutions per minute of the rotor can therefore be increased or decreased through the operation of the speed setting control. At the same time, only one drill-hole at the speed control mechanism will be facing the air intake bore. Which one of the two bores depends on which side of the grinding machine the speed setting control is connected with the regulator ring.
In order to be able to install the speed setting control in different positions, the casing is to be fitted on opposite sides with two fittings with which the speed setting feature can be connected with the regulator ring preferably with the aid of screws. One and the same top handle can therefore feature the speed setting control in different positions depending on the needs of the individual user. This is especially useful for left-handed versus right-handed users who operated the speed setting control with the index finger, so that the speed setting control can be moved on the left side of the machine for use by a right handed person and on the right side of the machine for a left handed person. The casing will therefore feature different holders and the regulator ring will for example feature a thread so that it can be connected with the speed-setting feature in various positions. Regardless of the position of the speed setting feature on the left or right side of the machine, the regulator ring will be moved with the same degree while this turning motion will correlate to the speed control mechanism.
Users with different hand sizes, especially male and female users, will be accommodated through at least two consecutive fittings on each side of the grinding machine through which the speed control feature can be connected with the regulator ring, preferably with the aid of screws. In connection with the shape of the top handle, which will be detailed at a later point, and the width of the top handle which tapers off there are two fittings on each side of the grinding machine which can hold the speed setting feature in place. This ensures as well, that different users, right handed and left handed users as well as users with different hand sizes, can uses this machine with just one hand, since the speed setting feature is always positioned within reach of the index finger. Due to the connection of the speed setting feature and the fittings, or more precisely regulator ring, it is possible to change the features of the top handle quickly and without additional replacement or supplementary parts.
To improve the handling of the grinding machine, it is also intended that the top handle is molded to accommodate a human hand by tapering off on its sides and by giving the covering a ergonomically curved surface. This enables a precise guiding of the grinding machine over the surface of the work object. The curved surface is fit to accommodate the inside of the hand while the speed setting feature is positioned within reach of the index- or middle finger. This especially makes it possible to apply consistent pressure onto the surface of the work object while being able to vary the speed of the grinding tool during the grinding process.
In addition, the top handle becomes functionally narrower in its width towards the supply connection. This shall enable users with different hand sizes, especially female and male users, to hold and guide the grinding machine, or more precisely the top handle, comfortably and safely during the work process. For this reason, the top handle features tapered sides, which allow the top handle to be held well by one hand.
In order to avoid an unintended operation of the grinding machine, it is intended that the grinding machine is equipped with a safety feature on its back which can block the operation of the top handle. The top handle can only be operated after the safety feature has been removed from its blocking position. It therefore prevents the holding clamp from being unintentionally moved towards the top handle, or more precisely the grinding tool. Therefore the holding clamp features a space, which corresponds with the fit of the safety feature.
A further functional development of the grinding machine is to equip the grinding machine with a vacuum connection that correlates to the grinding tool. This vacuum connection sucks away shavings and particles which were removed from the surface of the object during the grinding process so that they cannot get into the air or onto the object. For this reason, the vacuum connection sits right in the area of the grinding tool or better the protective casing.
In another version of the invention, the vitiated air connection and the vacuum connection are combined in one common connection. Thus, the shavings and particles, in other words the material that is being removed from the object, can be disposed directly via a combined connection. The grinding machine can also have a separate vitiated air connection and a separate vacuum connection.
The invention is distinguished by the fact, that it presents a portable grinding machine with which the surface of an object can be worked on by just one hand as an innovation. All safety-, control- and regulator features can be reached and operated single handedly. This is true for the on/off switch for the operation on the back of the top handle, an additional safety feature and especially for the speed control mechanism, which can be moved and operated with the index finger. The speed control feature can be detached from the top handle and set in at least four different positions for right- and left handed users as well as users with different hand sizes. The top handle is therefore not round but features a curved surface, also, the machine slowly increases in height from its back end to the front in a soft line, so that the user can put the entire hand on the casing and guide the grinding machine safely.