FR2539208A1 - Guard for precision drilling machine - Google Patents

Abstract

The pantograph links (3,4) operate in parallel, being pivoted at one end (1,2) to the machine and at the other end (10,11) to the guard (12). The drill (20) is raised and lowered through a rack and pinion by a lever (13), with spring assisted return. An auxiliary lever is connected to the pinion shaft and acts on a roller fixed to the guard. As the guard moves vertically the effective radius of the lever varies. Due to the position of the pivots behind the pivot of the operating lever, the movement of the guard is an amplification of that of the drill.

Description

 The present invention relates to a safety device for drills, and in particular for sensitive drills. It is known in fact that, despite their simplicity of design and their ease of implementation and use, drills, and more particularly sensitive drills, constitute very dangerous machines.

 The worker who works on such drills is seldom protected by a head covering or by a fishnet, and as a result his hair, or even his scalp, may be pulled out while he recklessly approaches the rotating chuck of the drill. In addition, it is common to see a worker holding his work in his hand, which, when it turns, can cause serious injuries, for example cuts and dislocations. For safety reasons, it should be a rule to tighten the part to be drilled in a vice-type workpiece holder; but, since it is long and difficult to mobilize this workpiece in the correct position, the worker prefers to hold the workpiece by hand, which involves the risks mentioned above.

 In addition, since the control lever of the drill is located to the right of the operator, the drilling torque is such that a workpiece held by the left hand laid flat will cause, at the time of its rotation, a significant dislocation of the operator's left hand D When it is assumed that the torque exerted by the drill bit is significant, the operator is helped by a companion, who, using his hands to imj: nobilize the holder piece, is then in danger.

There are a number of safety devices for drills, however, these known devices are generally difficult to use on sensitive drills. Examples of embodiments of known devices include removable screens actuated by pneumatic cylinders, for automatic drills. In such devices, means are generally provided to be guided by rails to allow the drilling aligned holes However, in the general case of single parts or small series s, the safety devices are limited to telescopic cylindrical casings mounted around the spindle of the drill, to protect the operators, and more particularly their hair .These cylindrical housings, of generally semi-circular section,
are of small diameter, and therefore the chips produced by the drill
are hampered in their release, and they strike the protective casing. it follows that the protective casings must besides serious and careful manufacturing, in order to avoid that they take play and that they do not get stuck
The present invention has set itself the objective of providing a safety device for sensitive drills which makes it possible to considerably increase the safety of the operator, by virtually eliminating the causes of serious accidents, without however harming the drilling the part to be machined. Indeed, it is essential that, taking into account the habits and requirements related to the drilling operation itself, the safety devices are designed and produced in such a way that the operator, aware of their usefulness and effectiveness, is not inclined to delete them in order to be able to work as in the past. For this purpose, a really usable safety device must meet the following criteria - need to always see the clamp clearly to be pierced, more particular
at the start of drilling - be, before this moment, fully protected against the dangers arising
both the rotation of the spindle of the drill; - easily operate the workpiece holder holding the workpiece, the elements
gripper being immobilized firmly in rotation, without the
torque opposing the spindle rotation results in an offset
from the center point.

 Furthermore, it is necessary that the safety device is designed to prevent the non-use of the various elements of the device.

 The invention therefore relates to a safety device for drills, in particular for sensitive drills, which comprises: a removable protective screen; a system for holding against the rotational movements of the part gripping assembly, and command and control means, this device being characterized in that said screen is mounted on an articulation system, for example of the type articulated parallelogram, designed so that the fixed axes of the levers of the articulation system are positioned behind the axis of the pinion drive pinion of the drill, which determines the rapid descent of the screen of protection, controlled by a lever fixed on the axis of the spindle, so that the actual drilling only begins when the protection is effective, in that the workpiece gripping system is kept against the movements of rotation by a rigid connection angularly, in order to obtain a gripping of a piece with easy movement, owing to the absence of torque, and in that the command and control means are designed so that said removable protective screen either obligato irement in place to perform a drilling operation, a dual-function sensor being provided for this purpose to control that the screen actually moves to come to position in safety function, and that the operator maintains a hand in contact with the operating handle of the workpiece gripping system, said handle being located outside the working area, while the other hand of the operator acts on the lowering lever.

 According to a characteristic of this invention, the angular rigid connection ensuring the rotation of the workpiece gripping system consists of a rule fixed on the workpiece grip and sliding in a pivoting yoke secured to the drilling table.

 Other characteristics and advantages of this invention will emerge from the description given below with reference to the appended drawings, which illustrate various embodiments thereof which are in no way limiting.

On the drawings
- Figure 1 is a schematic view, in side elevation, of a first embodiment of the invention;
- Figure 2 is a partial schematic view, in side elevation, of a variant of the invention;
- Figure 3 is a plan view of Figure 1
- Figure 4 is a partial view, in side elevation, of an exemplary embodiment of a security screen control means
- Figure 5 is a view similar to Figure 4> illustrating the operation of the security screen system according to the invention
- Figure 6 is a view similar to Figure 4, illustrating a variant of the invention
- Figure 7 shows yet another variant of the safety screen control device, viewed in side elevation
- Figure 8 is a plan view of a first embodiment of the device for holding the part gripping system in rotation
- Figure 9 is a side elevational view of Figure 8
- Figure 10 is a plan view of a second embodiment of the device for holding the workpiece gripping system in rotation
- Figure 11 is a plan view of a third embodiment of the device for holding the part grip in rotation
- Figure 12 is a side elevational view of the device shown in Figure ll
- Figure 13 shows, in plan, a variant of the invention applied to a battery of drills
- Figure 14 shows, schematically, in side elevation, the command and control means of the safety device according to the invention; and,
- Figure 15 shows schematically the electrical control diagram of the control means of the device according to the invention.

 Reference is firstly made to Figures 1 to 7s for the description of the removable protective screen of the device according to this invention.

 The security screen holder system is designed so that it can be produced either as an accessory adaptable to existing drills, or as an element forming an integral part of a drill. On the Figu # re 1, there is shown a drill with the original safety device according to the invention, while Figure 2 shows a drill according to the prior art on which has been mounted, as an accessory, a device according to this invention. Figure 3 is a plan view common to these two variants of the invention.

 security screen 12 present in planes the shape of a U. It is preferably made of a transparent, light and resistant material, for example acrylic glass, Oll or from a metal frame comprising a window closed by a material transparent This screen is mounted on an articulation system, produced here in the form of an articulated parallelogram comprising sets of double levers 3 and 4, articulated at 1 and 2 on the frame 7 of the drill, and at 10 and it on the protective screen 12. The essential difference between the two exemplary embodiments illustrated by Figures 1 and 2 lies in that, for each side of the device, the joints 1 and 2 of the levers 3 and 4 are, for the embodiment of Figure 1, provided by axes 5, 6 screwed into bosses forming an integral part of the body 7, while, in the embodiment of Figure 2, these axes 1 and 2 are mounted on bars 8 and 9 fixed to the body 7 using means s not shown.

 An articulated assembly is thus produced (screen 12, levers 3, 4) which, of light design, does not necessarily require balancing means.

 The articulated assembly is maneuvered by the lever 13, which also controls the movements of the spindle 20 by acting, by a rack pinion 14, on the rack 15 of the drill spindle sleeve, At the end of the drilling operation , the ascent of the spindle 20 and of the lever 13 is ensured by a spring (not shown in the drawing), generally in a spiral and with variable force. For the high position illustrated in Figure 1, this return spring can be adjusted to maintain, in addition to the spindle, protective screen 12, using a lever 16 (Figures 3 and 4) fixed on the axis of the rack 14, for example by pinching, and on which rests a support element integral with the screen 12, for example a roller or a roller 17.

It will be noted that, according to the invention, the points of articulation 1, 2, on the frame 7 of the articulated parallelogram constituted by the protective screen 12, and the levers 3 and 4, being located behind the axis 13 'of the lever 13, the slack vexent descent follows a law of speeds comprising two components a) first, the ratio of the levers a (radius of the rack pinion
14, Fig. 9) 3 and b (distance from the center of the radius of the pinion of the rack 14 to the axis of the Icr, wheel 17) is such that there is an amplification of the movement-
ment of descent of the screen 12 relative to the spindle 20 b) secondly, this speed is not constant. The angle of attack of the caster 17 on the lever 16 varies: at the high point, the center of the caster 179
which is placed on a circumference of center C (Fig. 5), such as the
radius C 17 is parallel and of length equal to levers 3 and 4, exerts a
very oblique action on lever 16. As a result, a small displacement
angle of lever 16 results in a displacement of large ampli
study of the wheel 17, therefore of the protective screen 12. At the end of the descent,
the lever 16 being in a position close to the horizontal, this effect
amplification is reduced, especially as the ratio a is lower
b
The low position of the protective screen 12 is defined by its contact against an adjustable stop, or against the workpiece gripping system (vice, for example), or against the table 19. It will be understood that, in this low position, the operator is protected.

In the variant illustrated in Figure 7, the quadrilateral formed by the levers 3 ', 4' and the screen 12, with the points of articulation 1, 2, 11, 12, does not constitute a rigorous parallelogram, the lever 4 'being larger than the lever 3', and the articulation points being placed in such a way that the safety screen 12 has its vertical front face for the high position
(in solid lines, in Fig. 7), and that this front face be inclined towards
the front, for the low position (in phantom, in Fig. 7), the levers
3 'and 41 then being in a position close to the horizontal. Such a variant
offers the advantage of enlarging the working area, thus increasing the walking lane
wise left to shavings driven in rotation.

We can consider a simplified variant, which can be
used in some cases. In this variant, the screen is mounted, by the intermediary of the two upper levers, in an angular position immutable by
relative to them, so that in the low position, we find the protective position
tion of the previous screen.

It was specified above that the points of articulation 1 and 2 of the levers of
the screen 12 were placed behind the articulation point 13 'of the control lever 13. This rear position of the articulation points 1 and 2 makes it possible to replace the lever 16 by a cam 16i, which acts the following way
In the high position (Fig. 6), the cam 16 ′ is in contact, by its doric cylindrical shape d, with the wheel 17. In this position, the force of the pnl rap spring does not intervene, and this force is just sufficient to raise the lever
13 and the spindle holder sleeve 20. Of course, during the ascent, it is necessary to slightly assist the lever 13, by pushing it slightly towards
the top, in order to overcome the low weight of the protective screen.

When the lever 13 descends, the cam 16 ′, by turning, after the
wheel 17 has crossed the angle e, maintains, by the form f, slightly concave of its profile, the screen 12, by means of the wheel 17, this form
concave allowing an even faster descent of the screen 12, at the start of the descent of the lever 13, When the screen 12 comes to a stop, the drilling operation can be carried out in the manner previously described; but, in this
case - and this constitutes the great advantage of the cam 16 'the return spring
retains the sensitivity it could have before mounting the device
of security. Of course, the cam 16 'is adjusted for the position corresponding to the maximum ascent of the spindle, and it is locked in
this position on the axis of the rack 14.

We will now describe the means for holding the clamping system.
the workpiece to be drilled (workpiece gripping system) against the rotational movements of the tightening torque. These means can be produced in various forms, their aim always being to prevent the workpiece carrier from being rotated.

 The embodiment illustrated in Figures 8 and 9 is the simplest solution. In this example, a vertical support 21 is fixed to the rear of the table 19, this vertical support being produced for example in the form of a guide maintaining the height position of the part 9 to avoid any lifting during the opening of the drill and the ascent of the spindle, and allowing the angular displacements, as well as the movements in translation of a rule 22, fixed on the sole of the part gripping device 23, represented here in the form of a vice placed. on table 19. Such an arrangement does not harm the positioning of the part P under the spindle of the drill.

When drilling part P9, the operator can safely hold the part gripping system 23 in this position. Indeed, the torque resisting the drill force is equal to the sum of two couples a) on the one hand, the couple g, dO at the force h, resulting from the friction of the sys
workpiece pick-up 23 on table 19, under the action of vertical force
of drilling and the weight of the clamping assembly9 and the force ç equal to
the force h (this force i passing through the axis of the support 21 and being directed
perpendicular to the straight line passing through this axis and that of pin 20
of the drill), the forces h and i acting on the lever arm 21-24 (j)
and, b) on the other hand, the friction torque K, which results directly from the action
of the vertical force on the table 19.

 This pair g + K, resistant to the force of the drill, is sufficient in most cases.

 The efficiency of the device thus described can between improved when the force h becomes low, in particular when the weight of the clamping assembly and the coefficient of friction are low, to prevent the workpiece gripping system 23 from tending to move in a direction opposite to the force h, the drill bit then participating in maintaining the part P in position. According to this improved variant, in accordance with the present invention, there is provided, under the sole of the part gripping device 23, one or more pads made of a material with a high coefficient of friction. This provides a more efficient system.

 The variant of the invention shown in Figure 10 also provides a satisfactory solution to the problem raised above. In this variant, the part gripping device 23 is connected, by two articulation points 26 and 27 provided on its sole, to two attachment points 28 and 29, integral with the table 19, via of an articulated assembly of the type used in the production of drawing apparatus. Such a device, based on an articulated parallelogram, keeps the part gripping device 23 parallel to a fixed direction, and the action of a torque exerted on the axes 26 and 27 gives no harmful translation reaction. As a result, during drilling, the drill acts ideally.

 According to another exemplary embodiment of the invention, this device is improved by implementing an equivalent system, composed of a combination of chair sprockets and chains, known for other applications.

This device has been shown in Figures 11 and 12.

 One or more levers, such as 30, are articulated around an axis 31, integral with the table 19 by a connecting support 32. One or more levers, such as 33, are articulated, by 7 gas 34, i these levers 30 , the levers 33 being mounted pivoting about an axis 35, fixed on the workpiece taking device 23. The axes 31, 34 and 35 respectively constitute, according to the invention, hubs of chain sprockets comprising the same number of teeth, of us, two, and a stage, respectively. The fleshy pinion 31 is connected to the first stage of the chain pinion 34 by a chain 36, and the second stage of the pinion 34 is connected, by a chain 37, to the pinion chain 35. The pinion 31 being immobilized in rotation, the pinions 34 and 35 therefore remain in an immutable angular position, whatever the position of the workpiece carrier 23.

 The torque resulting from the rotation of the drill is counteracted by the natural friction torque of the sole of the gripping device and by the reaction torque of the articulated system. Since these are only couples, the reaction on the drill is ideal.

 It will be noted that, in the case of the devices described above with reference to F # igures 10 to 12, the friction torque K can be zero, without this resulting in any inconvenience. This makes it possible to obtain a zero coefficient of friction between the workpiece gripping system 23 and the table 19, which results in an ideal smoothness and freedom of movement of the workpiece gripping system.

The work of the part gripping system is much easier, thanks to the devices according to the invention, owing to the absence of torque in front of the operator exerted by the operator's left hand,
FIG. 13 shows an example of application of the invention in the case of a battery of drills. In this embodiment, preferably use is made of an arrangement whose design is similar to that of drawing devices with linear guides.

 A socket 37, preferably ball-type t-ype and without play, is slidably mounted on a bar 38, fixed on the table 40 by means of two lateral supports 39, 39 'sliding in an internal guide means, provided in the part gripping device 23, a bar 41, integral with the socket 37, holding the part to be drilled P in a well-defined orientation. Such an arrangement allows, without hindrance, the passage of the part gripping device 23 under the different pins 42. This arrangement implements the well-known principle of the Olshann seal.

We have seen, in the preamble to the present description, that it was necessary to provide means for command and control of the protective screen and of the spindle, in order to allow the device to be used without constraint according to the invention. These control means can be electrical, electronic or pneumatic. The nonlimiting exemplary embodiment described below, with reference to Figures 14 and 15, is based on electro-mechanical elements s O
In reality, it is not possible to define a basic principle valid for all applications. It is necessary to reconcile too many differences in use - series; small series 9 unit parts - vice clamping; during assembly - flat, high, small or large parts, etc.
For these reasons, we may have to accept or refuse certain prohibitions. Experience and common sense decide it.

 The embodiment described below represents a case of maximum security. Without being a single example, it can serve as a basis.

In this example, the security package is controlled by different
sensors (Fig. 14 and 15). A sensor 43 verifies that the protective screen 12 is placed above a position situated at a sufficiently large distance from the high point (by making it, for example, check the passage of the lever 3). movement control of the gripping system and that of the lowering lever 13, two naturally open contacts 45 and 46 are provided, which happen to be closed, one by the left hand placed on the handle, the other by the holding the lowering lever. These contacts can obviously be of any type, and in particular electronic contact.

Via the control button B (Figure 15), a contactor
C is energized, firstly through contact E, which is closed because contact E is supplied through sensor 43, by general energization.

 The indicator lamp 47 comes on through contact C, showing that the drill is under effective voltage.

 When the operator acts on the lever 13 to pierce, the protective screen 12 descends.

 When the arm 3 stops informing of its presence the sensor 43, the coal actor R is actuated through the contact C and the contact E, which closes.

Contactor R is then powered by its auto-contact. Lamp 47 is always lit by R and E.

 After a few fractions of seconds, the naturally closed contact with delayed opening of R cuts off the self-supply of Ç. The motor M of the drill is then supplied through contact R and sensors 45 and 46; the worker can drill. The engine stops if he does not maintain these sockets.

On ascent, the contactor R drops when the sensor 43 notes the passage of the lever 3 thus actuating the contactor E. -e contact E cuts the self-supply of R,
Only contact E remains energized for control.

it should be noted that the operator must then press button B for each descent. This is the maximum safety cycle,
By removing the delayed opening contact R, the contactor C would remain energized, and, in this case, the motor M would rotate each time the screen 12 was lowered, which can be done by bypassing through a switch. As such a possibility can be dangerous, since the lowering of the spindle by traction (tightening of the mandrel, for example) would start the machine, a timer could cut off the supply of C after a few seconds of non-use.

 We see that we can remove prohibitions, and that this scheme can be adjusted.

 The main thing is that the screen controls the rotation of the spindle of the drill by its descent, which prohibits its immobilization at the top. In addition, it must be at the top to allow power up.

 It remains to be understood that this invention is not limited to the various embodiments described here, but that it encompasses all variants thereof.

Claims (10)

 1 - Safety device for drills, and in particular for sensitive drills, which comprises: a removable protective screen; a system for holding against the rotational movements of the part gripping assembly, and command and control means, this device being characterized in that said screen (12) is mounted on a system of articulation (3, 4) designed so that the fixed axes of the articulation system are positioned behind the axis of the pinion drive pinion (20) of the drill, which determines a rapid descent of the screen protection, controlled by a control means (16, 16t) fixed on the spindle axis so that the actual drilling does not start until the protection is effective, in that the workholding system (23) is kept against rotational displacements by an angularly rigid connection (21, 22), designed so as to obtain gripping of a piece with easy movement due to the absence of torque, and against uprisings at the outlet of the drill and during the ascent of the spindle, and in that the means of comm ande and control are designed so that said removable protective screen is necessarily in place to perform a drilling operation, a dual-function sensor (43) being provided for this purpose, to check that the screen (12) effectively moves in order to come to position itself as a safety function, and to con tain that the operator maintains a hand in contact with the handle of my work of the gripping system, this handle being located outside the work area , while the other hand of the operator acts on the lowering lever (13).  2 - Device according to claim 1, characterized in that said articulation system of the protective screen (12) is produced in the form of an articulated parallelogram, comprising a set of levers (3, 4) articulated on the one hand on the body (7) of the drill, and, on the other hand, on the screen (12).  3 - Device according to one of claims 1 or 2, characterized in that the lower articulation levers (4 ') of the protective screen are longer than the upper levers (31), which allows, in the low position , to obtain an enlargement of the security zone.  4 - Device according to any one of claims 1 to 3, characterized in that the means for controlling the downward movement of the protective screen (12) consist of a lever (16) fixed on the axis of the created -rnaillere (14) of the drilling lever (13), on which a support element tbien integral with the screen (12) rests, this support element being able to be produced in the form of a caster (17).  5 - Device according to any one of claims 1 to 3, characterized in that the means for controlling the downward movement of the protective screen (12) consist of a cam (16 ') comprising a cylindrical part (d ) ensuring the high position of the screen, and a concave part (f), defining the law of the downward movement.  6 - Device according to any one of the preceding claims, characterized in that the rigid connection ensuring the rotation of the part gripping system consists of a rule (22) fixed on the sole of the part gripping system, this rule sliding in a pivoting holding means (21), mounted at the rear of the table (19) of the drill, which prevents the lifting of the part 2 at the outlet of the drill and at the ascent of the spindle (20) .  7 - Device according to any one of claims 1 to 6, characterized in that the rigid connection ensuring the maintenance in rotation of the part gripping system consists of an articulated assembly with double parallelogram (26, 272 28, 29) .  8 - Device according to any one of claims 1 to 6, characterized in that the rigid connection ensuring the maintenance in rotation of the part gripping system consists of an articulated assembly which comprises two levers (30, 33), two link and chain sprocket systems (31, 34, 35; 36, 37), the two end sprockets being, one fixed (31), the other (35) integral with the part gripping system, and the pinion (35) and the pinion (34) remaining in an invariable angular position, regardless of the position of the gripping system.  9 - Device according to any one of claims 1 to 6, characterized in that the means used to ensure the angular stiffness of the part gripping system consists of an Oldham seal, which forms the sliding part gripping system on a bar (41), itself secured to a guide piece (37) sliding on a second bar (38) held on the table (40).  10 - Device according to any one of the preceding claims, characterized in that the security system is controlled by a first sensor (43), which verifies that the protective screen (12) is placed above a position located at a sufficiently large distance from the high point, and by two other sensor-contractors (45-46), fixed respectively on the handle for controlling the movement of the gripping system and on that of the lowering lever, these two contacts (45, 46), normally open, being closed, one by the operator's left hand, placed on said handle, the other by holding the lowering lever.