WO1991011295A1

WO1991011295A1 - Automatic screwer

Info

Publication number: WO1991011295A1
Application number: PCT/IT1991/000003
Authority: WO
Inventors: Nerio Bentivogli
Original assignee: Ober Utensili Pneumatici S.R.L.
Priority date: 1990-01-29
Filing date: 1991-01-23
Publication date: 1991-08-08
Also published as: IT9004717V0; IT9004717U1; IT224918Z2

Abstract

In an automatic screwer a tubular housing (1) features a channel (4) provided with pliers (8) for keeping a screw (7) inserted in the channel while a shell (9) contains a pneumatic motor for rotating a blade (10) that can be inserted in the head (7b) of the screw (7) with a pneumatic distributor connected with two chambers (12, 13) and a lever (20) linked to the distributor (35) to set under pressure either the return chamber (12) or the final advancement chamber (13). An initial advancement chamber (15a) is connected with a source (100) of compressed air through an intake valve (30) and a piston (14) slides in the chamber (15a). The intake valve is controlled so as to set under pressure the initial advancement chamber (15a) with advancement of the piston (14) and engagement of the blade (10) with the head (7b) of the screw (7), or with discharge of the initial advancement chamber (15a), according to the release or the operation of the lever (20).

Description

AUTOMATIC SCREWER

TECHNICAL FIELD

This invention relates to the technical field of automatic screwers, either with a supporting structure or portable.

BACKGROUND ART

Such screwers comprise a cylindrical tubular housing whose front end is associated with an operating head featuring a through axial channel. The front portion of said head is defined by pliers, operating symmetrically to said channel, designed to elastically restrain a screw inserted into the channel either automatically or manually, through a feeding mouth provided in the head.

Said screw is positioned in such a way that its shank protrudes out of the pliers. The screw head is to be engaged by a blade located inside said housing; said engagement is made possible by the axial translation given to the blade either manually, or through handling means located in the housing. The blade is drawn into rotation by the action of motor means, located in said housing, actuated in a suitable phase relationship with the axial translation of the same blade.

The combined action of the rotation and the translation of the blade allows the engagement of the screw with the relative seating (or zone) where it is to be fastened, with the contemporary disengagement of the same screw from the pliers.

In some cases, e.g. with self-threading screws, while the operator is looking for the point where the tip of the screw is to be driven in, in order to locate that point as much exactly as possible, the same screw, not yet subjected to the action of said blade, undergoes axial thrusts not suitably offset by the pliers.

This brings about the axial return of the screw into the head channel, with all the drawbacks known by the experts in the field.

Some technical solutions are known, which on the one hand avoid the axial return of the screw, but on the other hand bring about further drawbacks. In a known solution, upstream of the pliers at least a rocking lever is provided, so to allow the passage of the screw in the channel from inside outwards, but not the reverse, thus acting as a ratchet gear. In practice, said lever is struck by the screw, thus, with the use of the screwer, it tends to break.

In another known solution, the operating head is axially movable as to the housing, through a pneumatic jack external to said housing and head. Upon the insertion of the screw into the channel of the head, this latter results to be at the maximum distance from the housing. After said insertion, the head is moved closer to the housing so to allow the interception of the screw head against the blade; thus the axial return of the screw into the channel is avoided, also by the fact that the axial movement of the blade is performed manually.

That solution turns out to be particularly complex, as well as cumbersome; the moving parts of the screwer require a suitable operating space, with all the drawbacks that this brings about.

DISCLOSURE OF THE INVENTION

One of the objects of the present invention is the provision of an automatic screwer which, besides its specific purposes, avoids the axial return of the screw, through a technical solution which turns out to be of simple construction, functional, reliable, and does not involve any parts in movement externally to the housing of the same screwer.

Another object of this invention is to improve said screwer so that it may be usefully associated with a screw dispenser designed to feed the same screwer automatically.

A further object of this invention is to provide a screwer which, besides the above-mentioned features, turns out to be universal, i.e. it may be fed either automatically or manually.

The above-mentioned objects are accomplished by that certain construction and arrangement of parts to be hereinafter more specifically pointed out and claimed.

The improvements provided allow to stabilize the position wherein the screw is kept elastically by pliers, i.e. with its shank protruding from the pliers, independently from the presence or the absence of axial stresses acting on the screw and directed towards the inside of the screwer.

Consequently, the present screwer may be advantageously used anyway, particularly in those situations requiring, for optimal results, to exert an axial thrust on the screw, from outside inwards, before screwing.

Further the improvements do not involve any parts moving externally, therefore the operating space required when the screwer is to be used depends exclusively on its size.

Moreover the improvements provided are feasible both for automatic-feed screwers, and for manual-feed screwers, and indifferently for fixed or portable screwers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein: - Figures 1,2,3 are all diagrammatic views of longitudinal sections of the present screwer showing this latter respectively in the operating position, in the automatic screw feeding position, and in the rest position; - Figures 4a, 4b, 4c, 4d show diagrammatic views of longitudinal sections of the head of the present screwer, illustrating significant phases of the manual feeding of this latter.

MODES FOR CARRYING OUT THE INVENTION

Referring to Figs. 1,2,3, the numeral 1 generally designates a cylindrical housing having its back end closed by a wall 2 and being provided, in the other end, with an operating head 3 featuring a through axial channel 4. In the channel 4, in central position, has its outlet a feeding mouth 5 (provided in the head 3) associated, through a duct 6, with an automatic dispenser 50 of screws 7.

The front portion of the head 3 is defined by pliers 8 (illustrated schematically, as they are already known) operating symmetrically as to the channel 4; the function of said pliers is to elastically restrain a screw 7, with this latter oriented as shown in fig.3, i.e. with its shank 7a protruding from the same pliers.

In the axial hole 15 of the housing 1 is located a cylindrical shell 9 containing a pneumatic geared motor (not illustrated) and a friction assembly (also not illustrated) associated with a blade 10, freely inserted into the channel 4, whose front end 10a has a shape complementary to the head 7b of the screw 7, in order to engage with this latter screw head .

The shell 9, which may slide axially inside the housing, is centrally provided with a shoulder 11 defining, in a relative portion of the housing hole 15, two chambers 12,13, respectively for the return of the shell and for the final advancement of the latter (as will be hereinafter more fully explained).

The back portion 9a of the shell 9 slides in the back portion 15a of the hole 15, or initial advancement chamber of the shell itself, closed transversally by the wall 2. In the chamber 15a slides sealingly a piston 14.

The chamber 15a, on the side of the wall 2, is connected with a duct 24 which, by the interposition of a valve 30, is connected with a source 100 of compressed air.

The chambers 12,13 are connected, through relative ducts 12a, 13a, with a cylinder 16 made in a body 17 integral with the housing; in said cylinder a feeding duct 18, connected with said source 100 of compressed air, has its outlet.

In the cylinder 16 is inserted a distributor valve 19 which may be operated manually by the operator through a lever 20 restrained to the body 17, in contrast with a spring 21 inserted in the cylinder

16; the cylinder 16 and the valve 19 define a pneumatic distributor 35.

With the lever 20 lowered (fig.l) the distributor 35 allows to put only the chamber 13 under pressure, while with the lever 20 raised (figs. 2 and 3), the same distributor 35 allows to put only the chamber 12 under pressure. In the surface defining the hole 15 there is an annular groove connected with a duct 23 associated with a control unit 40 controlling the distributor 35 and the valve 30. The operation of the screwer is described here below, referring to figs. 1,2,3.

The rest position, i.e. the condition of interval between a screwing and the subsequent one, is illustrated in fig.3. The shank 7a of the screw 7 results to be protruding from the pliers 8, and the relative head 7b rests stably on the front end 10a of the blade 10^' which is supported by the shell 9 with this latter kept in a characteristic position H by the piston 14 acting on the back end 9b of the same shell.

In detail, in the position of fig.3 the lever 20 is released, therefore the return chamber 12 is under pressure, and the chamber 15a is under pressure as well; with equal pressure, since the thrust section of the chamber 12 is remarkably smaller than the thrust section of the piston 14, consequently it is this latter that keeps the shell forward up to the said position H defined by the stroke of the same piston against a ring 25 (inner position I of the piston) .

The operation of the lever 20 (made by the operator, fig.l) brings under pressure the final advancement chamber 13, through the distributor 35.

This brings about the advancement (direction F) of the shell 9, and of course of the blade 10, as well as the actuation (in a way already known, thus not illustrated) of the geared motor with dragging into rotation (direction M) of the blade 10 and of the screw 7, with which the latter is engaged.

Consequently to the advancement of the shell 9, according to F, a slot 26 made in the back portion 9a of the same shell 9, and connected with the chamber 13, goes to overlap said annular groove 22; thus the duct 23 is interested by a pressure signal (relative to the chamber 13) detected by the control unit 40.

As a consequence of such signal (maximum value of pressure in the chamber 13) the control unit 40 acts on the dispenser 50, in order to prearrange the selection and the sorting out of a screw 7, and actuates the valve 30 so to bring about the discharge (arrow P) of the chamber 15a of the piston 14. At the end of the screwing, position K in fig.l (signalled by the mechanical release of the friction) the operator releases the lever 20, which , through the distributor 35, brings again the return chamber 12 under pressure; this allows the backing (direction G) of the shell 9 up to the position X (fig.2); such backing is not obstructed by the piston 14 (since the relative chamber 15a is discharged) which on the other hand is pulled by the back portion 9a of the same shell against the wall 2 (outer position E of the piston) .

With the lever 20 released, the chamber 13 is discharged; through the slot 25 and the groove 22 also the duct 23 gets discharged, which is detected by the control unit 40 which acts on the dispenser 50; this latter, consequently, in a suitable phase relationship with the backing of the shell 9, carries out the "automatic shooting" (direction V) of a screw 7 into the duct 6 ( fig . 2 ) .

Said screw, through the feeding mouth 5, goes to take place between the pliers 8, since it is not obstructed by the blade 10 which is in its most backward position (fig.2).

In relationship of phase with the "shooting" of the screw 7, the dispenser 50 actuates the valve 30 so to restore, through this latter, the connection of the chamber 15a with the source 100 of compressed air. This brings about the translation (direction F) of the piston 14 (together with the shell 9) up to the stroke 25 (position I of the piston); then said position H is reached again, wherein the front end 10a of the blade 10 engages the head 7b of the screw 7. As a consequence of said engagement the return of the screw 7 is prevented even in presence of axial stresses acting on this latter and directed inwards; in other words, the shank 7a of the screw 7 is anyway kept external to the pliers 8 with all the obvious advantages involved.

The screwer being the object of this invention may also be used without the dispenser 50.

It is sufficient to provide, in the head 3, for a slit 27, leading to the channel 4 on one side, and accessible from outside on the other side; said slit results to be partially covered by a spring elastic element (or leaf spring) 28: please see figs. 4a, 4b, 4c, 4d.

In that different construction the control unit 40 shall act on the valve 30, so to carry out the cycle described above; in particular, it shall provide for actuating the valve 30 with a predetermined delay as to the detection of "zero" pressure in the chamber 13.

The operator shall have to introduce the screw manually, between a screwing and the subsequent one (so to comply with said predetermined time) into the slit 27 as illustrated, in detail, in figs. 4a, 4b, 4c, 4d.

In the example illustrated, the- valve 30 and the dispenser 50 are controlled by the control unit 40 of pneumatic type.

The technical solution described above may be usefully associated with electric means for controlling the valve 30, interlocked with suitable sensor means for detecting the characteristic positions of the shell 9, e.g. the above-mentioned characteristic positions H, K and X.

INDUSTRIAL APPLICABILITY

By means of the proposed technical solution it is possible to provide an automatic screwer which, besides its specific purposes, avoids the axial return of the screw. Therefore it is possible to obtain a screwer that turns out to be of simple construction, functional, reliable, and that does not involve any parts in movement externally to the housing.

Further by using this invention it is possible to manufacture a screwer that can be usefully associated with a screw dispenser designed to feed it automatically, but can also be fed manually. More generally the screwer so obtained can be used anyway, particularly in those situations requiring, for optimal results, to exert an axial thrust on the screw, from outside inwards, before screwing.

Claims

1. Automatic screwer, of the type comprising: a cylindrical tubular housing (1), an end of which defines an operating head (3) , featuring a through axial channel (4), whose front portion is defined by pliers (8), located symmetrically to said channel (4), designed to elastically restrain a screw (7), oriented with its shank (7a) external to the same pliers, inserted in said channel through a feeding mouth (5) provided in said head (3); a cylindrical shell (9) slidably housed in said housing (1), containing pneumatic motor means for rotating a blade (10) which is engaged frontally with said shell, freely inserted in said channel (4) and featuring the relative front end (10a) shaped complementary to the head (7b) of said screw (7), said shell (9) featuring centrally a shoulder 11 sealingly sliding in two consecutive chambers (12,13) respectively for return and final advancement, defined by the axial hole (15) of said housing (1); a pneumatic distributor (35) made in a body (17) integral with said housing (1), connected with said two chambers (12,13) as well as to an external source (100) of compressed air; a lever (20) operated manually, articulated with said body (17), acting on said distributor (35) to set under pressure, when released, the return chamber (12), and to set under pressure, when operated, the final advancement chamber (13); said screwer being characterized in that it comprises: an initial advancement chamber (15a), defined laterally by the back portion of the through hole (15) of said housing (1), and transversally by the closing wall (2) of this latter on one side, and by the back head of said shell (9), on the other side, with said chamber (15a) connected with said source (100) of compressed air by interposition of an intake valve (30); a piston (14) sealingly sliding in this latter chamber (15a) between .two limit positions, external (E) and internal (I), respectively identified by the stroke of the same piston (14) against said closing wall (2) and against a striker (25) provided, in said initial advancement chamber, said piston (14) featuring a thrust section greater than the thrust section defined by the portion of said shoulder (11) facing said return chamber (12); means for controlling said intake valve (30), having the purpose, in relationship of phase with the release of said lever (20), to put under pressure said initial advancement chamber (15a) with advancement of the piston (14) up to said inner position (I) and consequent dragging forward of said shell (9) up to the engagement of the front end (10a) of the blade (10) with the head (7b) of the screw (7) restrained elastically by said pliers (8), and also having the purpose, in relationship of phase with the operation of said lever (20), to start the discharge of said initial advancement chamber (15a).

2. Screwer according to Claim 1, characterized i that the means designed for controlling said intake valve (30) comprise means for detecting the pressure value in said final advancement chamber (13), connected with a pneumatic control unit (40) which, after detecting pressure in this latter chamber, stops said intake valve (30), and in case of lack of pressure in said chamber (13) actuates, with a predetermined delay, said intake valve.

3. Screwer according to Claim 1, providing a dispenser (50) for the automatic feeding of said feeding mouth (5) characterized in that the means designed for controlling said intake valve (30) comprise: means for detecting the value of pressure in said final advancement chamber (13) connected with a pneumatic control unit (40), which upon detection of pressure in said final advancement chamber (13) stops said intake valve (30) and prearranges for sorting out a screw in said dispenser (50), and as a consequence of the lack of pressure in said chamber (13) allows said dispenser to "shoot" a screw towards said feeding mouth (5); means for sensing the "shooting" of said screw, having the purpose to actuate said intake valve (30).

4. Screwer according to Claim 1, characterized in that said feeding mouth (5) consists of a slit (27) provided in said operating head (3), partially closed, corresponding to its outward portion, by elastic means (28).

5. Screwer according to Claim 1, 2 or 3, characterized in that the means for detecting the pressure in said final advancement chamber (13) are defined by an annular groove (22), made in the surface delimitating the axial hole (15) of said housing (1), made communicating with a duct (23) connected with said pneumatic control unit (40), and by a slot (26), made in the lateral surface of said shell, suited to allow said chamber (13) to communicate with said groove as a consequence of the axial translation of said shell.

6. Screwer according to Claim 1, characterized in that the means designed for controlling said intake valve (30) consist of electric means interlocked with means for sensing the positions of said shell (9) .