US2987748A - Doctors for paper and like machines - Google Patents

Description

June 13, 1961 H. E. B. SCOTT 2,987,748

DOCTORS FOR PAPER AND LIKE MACHINES Filed April 2. 1959 Unite States atent 2,987 748 DOCTORS FOR PAPER AND LIKE MACHINES Harold Eric Baliol Scott, Heath, Weybridge, England, assignor to Vickerys Limited, London, England Filed Apr. 2, 1959, Ser. No. 803,693 Claims priority, application Great Britain June 9, 1958 12 Claims. (Cl. 15-256.5)

front, i.e. from the side of the holder nearer the roll. The i holder is normally carried, in use of the doctor, on a support which is biased by a spring, by gravity or by fluid pressure so that the blade bears on the surface of the roll to be dootored, the support being capable of rocking movement to enable the doctor blade to be lifted off the roll. Especially when the blade is so mounted that, when in service, it extends in a downward direction it must be prevented from falling out of the holder when it is lifted off the roll, as otherwise there would be serious risk of injury to personnel and of damage to the plant to b doctored.

It has hitherto been the practice to provide on the underside of the doctor blade, the expression underside being used herein to designate the side of the doctor blade nearer the roll, rivets or other projections which engage in a longitudinal slot in the holder, the lip constituting the front of the slot being formed with gaps through which the rivets may be passed for the purpose of introducing the blade into, or withdrawing it from, the holder and the blade being slid endwise, preparatory to placing the doctor in service, to bring the rivets out of register with the gaps. Difiiculty, however, is often experienced in removing the blade fromthe holder after a period of service owing to dirt accumulated in the slot in the holder obstructing the endwise movement of the blade in the holder required to bring the rivets back into engagement with the gaps. It is the object of this invention to obviate this disadvantage. The invention provides a doctor for the rolls of paper making or like machines, comprising a doctor blade and an elongated holder supporting the rear edge of the doctor blade, the blade being normally retained against forward a withdrawal from the holder by spring tongues provided,

either on the rear edge of the blade and engaging a longitudinal groove in the holder, or on a member retained in the holder and engaging a longitudinal groove in the blade, said blade being capable in either case after it has been lifted off the roll, of limited rocking movement in relation to the holder to disengage the spring tongues from the groove and to permit of forward withdrawal of the blade from the holder.

Where the blade is of thin metal, the spring tongues are preferably downwardly bent at intervals along the rear edge of the blade and engage in alongitudin'al' groove in the holder beneath the blade.

Where, however, the blade is of thick non-metallic material, a longitudinal groove is providedin the blade near its rear edge and preferably on its upper surface for cooperation with spring tongues on the forward edge of a keep plate retained in the holder.

A general object of this invention is to provide doctors which are reliable and safe'in operation and which permit safe and easy removal of the blade for servicing.

Another object of the invention is to provide a doctor Patented June 13, 1961 ice in which a single holder is capable of holding blades of very diflierent thicknesses.

A further object of the invention is to provide a doctor in which the same holder is capable of retaining ditferen types of blades by the use of an adaptor.

Other objects and advantages of the invention will be come apparent and the invention will be fully understood from the following description and the accompanying drawing, in which: Y

FIG. 1 is a side elevation of one embodiment of the invention; Y 1 1 FIG. 2 is a partial underside plan view of the keep plate of the doctor shown in FIG. 1;

FIG. 3 is a side elevation of a second embodiment; and

FIG. 4 is a partial underside planview of the blade of the doctor shown in FIG. 3.

Like reference numerals indicate like parts throughout the figures.

Both forms of doctor shown in the drawings are of the general character described in British Patent No. 7 52,098 and US. application Serial No. 475,083, the holder being constituted by upper and lower parts 10, 11 suitably at tached together, as in the above-mentioned patent, for example. The lower part 10 of the holder is formed near the front with a longitudinal groove 12 extending throughout its length.

In the construction shown in FIGS. 1 and 2 the blade 13 is of thick non-metallic material while in the other construction the blade 113 is of thin metal. In both cases, a pressure plate 14 bears against the blade for it's full length, and a keep plate 15 situated below the pressure plate overlies the rear edge of the plate and provides clearance permitting the blade to float. The forward edge of the keep plate 15 is bevelled as shown at 16." The pres sure plate 14 has a series of downwardly depending retaining projections 24 which extend through holes inthe keep plate into a longitudinal slot 25 in the holder.

In the case of the doctor shown in FIGS. 1 and 2 the blade 13 has a longitudinal groove 17 in its upper surface situated near its rear edge and extending for its full length. The forward edge of the keep plate 15 is formed at intervals, e.g. of 3, 4 or 5 feet, with cutaway portions 18 between each pair of which is situated a downwardly bent spring tongue 19. These spring tongues 19 extend downwardly into the groove 17 in the blade, as shownfso as to restrain the blade against forward withdrawal from the holder. When, however, the doctor has been withdrawn from the roll, it can be rocked about the upper end of the lip 20 on the holder which constitutes the front of the groove 12 and against the pressure exerted by the pressure plate 14 and the spring tongues of the keep plate 15, sufficiently to disengage the tongues 19 from the groove 17 and allow the blade to be withdrawn forwardly from the holder. The rear edge of the blade is bevelled at 21 on its upper surface to assist the passage of the blade into the holder past the tongues 19 when the blade is inserted into the holder. 7

In the doctor shown in FIGS. 3 and 4, cutaway portions 118 are formed at intervals in the rear edge of the blade 113, a downwardly bent spring tongue 119 being provided between each pair of cutaway portions. Ths tongues 119 engage in the groove 12 so as normally to prevent the blade from being withdrawn forwardly from the holder. The blade 113 can, however, be rocked about the lip 20 and against the pressure exerted by the pressure plate 14 and the spring tongues of the blade to disengage the tongues 119'from the groove 12. i The keep plate 15 in this case has nospring tongues at its forward edge.

It is often necessary to use blades of a different thickness or material when a change :is made in the product being manufactured or when the-roll to 'bedoctord is replaced by one of a different material or hardness. This usually necessitates replacing the complete blade holder by one which is suitable for the new blade. Also, in some border-line cases, it is ditficult to predict whether a thin metal blade or a thick composition blade will give the most satisfactory results, and to change the blade holder is a long and costly matter and can only be done during the week-end when the paper machine is shut down.

Provision for overcoming these difliculties is made in the doctor according to the invention by reason of the fact that the groove 12 in the holder has a wide bottom and a narrow top, being of dovetail shape. When a thick composition blade 13 is to be replaced by a thin metal blade 113, the exchange can be made utilizing the same blade holder by inserting a dovetailed make-up piece 26 endwise into the groove 12, the upper portion 27 of which is of thickness appropriate to make up for the difference in thickness between thick and thin blades.

With this arrangement once the blade holder has been fitted to the doctor beam or support and lined up true with the roll, either thick composition blades with retaining grooves and a cooperating keep plate with spring tongues can be fitted or thin blades with spring retaining tongues and a plain keep plate can be used after the dovetailed make-up piece has been fitted in position. This change can be made in a very short time merely by sliding out the parts not required and replacing them with alternatives without affecting the alignment of the doctor with the roll. Various thicknesses of the blade can be used by providing a series of dovetailed pieces of varying height.

The advantage of this arrangement is that there is no need to keep a multiplicity of heavy extruded sections of blade holder in stock to accommodate blades of different thicknesses. One pair of blade holder sections, with the requisite number of light dovetailed pieces, is all that is required.

The groove 12 and make-up piece 26 need not necessarily be of dovetail section. Any other convenient undercut section can be used, provided the make-up piece is prevented from lifting out of the groove. The make-up piece need not be continuous but can consist of several short lengths butted together.

The blade may have a feed-in rivet 28 projecting from its undersurface at one end and near its rear edge. This assists in endwise feeding of the blade into the holder in applications, e.g. to drying cylinders of a paper machine, where it is impossible to insert the blade into the holder from the front. It is also useful for forward feeding into the holder of very long blades which otherwise require the services of several men spaced along the length of the blade. With the feed-in rivet, only one man is required. He just hooks the rivet into the groove 12 in the holder. This holds one end of the blade in position and the workman can then move along the blade fitting it into position bit by bit.

To remove the blade forwardly, it is first slid endwise by about 1 inch until the rivet is disengaged from the groove 12 and the blade can be shaken, while applying a forward pull, until it comes clear of the holder.

It will be appreciated that the spring tongues, whether they are provided on the blade or on the keep plate, do not positively retain the blade in position in the holder but are able to yield, when the blade is clear of the roll and is rocked sufficiently in relation to the holder, to permit of forward removal of the blade.

While I have shown and described two particular embodiments of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim is:

1. A doctor for a roll of-a papermaking or like machine, comprising a doctor blade elongated in a direction parallel to the axis of the roll and having a forward edge adapted to engage the roll and a rear edge remote from the roll, and an elongated holder in engagement with and supporting the rear edge of the blade and having a longitudinal groove beneath the rear end of the blade, the blade having spaced downwardly bent spring tongues at its rear edge which extend into and engage in said longi-- tudinal groove, a pressure plate disposed above the blade, projecting forwardly from the holder, having its rear edge retained in the holder and bearing against the upper surface of the blade throughout substantially the whole of its length at a region of said upper surface intermediate the front and rear edges of the blade, and a keep plate disposed beneath the pressure plate and projecting forwardly over the groove, the spring tongues normally cooperating with the groove to prevent forward withdrawal of the blade from the holder but being disengageable from the groove by rocking the blade about a longitudinal axis thereof when the blade has been lifted off the roll.

2. A doctor according to claim 1 wherein the blade has a downwardly extending feed-in rivet at one end near its rear edge for engagement with the longitudinal groove in the holder.

3. A doctor according to claim 1 wherein said blade is a thin metal blade and the holder has a longitudinal groove and a grooved make-up piece having a crosssection corresponding to that of said longitudinal groove in the holder, to permit the holder to accommodate said thin metal blade, said spring tongues being in engagement with the groove in the make-up piece, the make-up piece being shaped so as to be removable from the groove in an endwise direction but not upwardly.

4. A doctor according to claim 3, wherein the longitudinal groove of the holder is of dovetail cross-section.

5. A doctor according to claim 3, wherein the blade has a feed-in rivet at one end near its rear edge for engagement with the longitudinal groove in the holder.

6. A doctor for a roll of a papermaking or like machine, comprising a thick non-metallic doctor blade elongated in a direction parallel to the axis of the roll and having a forward edge adapted to engage the roll and a rear edge remote from the roll, said blade having a longitudinal groove in its upper surface near its rear edge, an elongated blade holder supporting the rear edge of the blade, a pressure plate disposed above the blade, projecting forwardly from the holder, having its rear edge retained in the holder and bearing against the upper surface of the blade throughout substantially the whole of its length, and a keep plate disposed beneath the pressure plate and projecting forwardly over the groove and having at its forward edge spaced, downwardly bent spring tongues engaging the groove in the blade, the spring tongues normally cooperating with the groove to prevent forward withdrawal of the blade from the holder but bein disengageable from the groove by rocking the blade about a longitudinal axis thereof when the blade has been lifted off the roll.

7. A doctor for a roll of a papermaking or like machine, comprising a doctor blade having an elongated width in a direction parallel to the axis of the roll and having a forward edge adapted to engage the roll and a rear edge remote from the roll, and an elongated blade holder in engagement with and supporting the rear edge of the blade, the blade and holder having retaining means including a groove and a plurality of spring tongues which are disposed along the width of the blade and inclined to the plane of the blade and engaging the groove to retain the blade against forward withdrawal from the holder when the blade is in its normal roll-engaging position in relation to the holder, the retaining means and holder enabling the blade to have a limited rocking movement in relation to the holder about a line parallel to the edges of the blade to disengage the spring tongues from the groove and thereby permit forward withdrawal of the blade from the holder.

8. A doctor for a roll of a papermaking or like machine, comprising a doctor blade having an elongated width in a direction parallel to the axis of the roll and having a forward edge adapted to engage the roll and a rear edge remote from the roll, and a blade holder in engagement with and supporting the blade along a line thereof parallel and close to its rear edge, said blade and bolder including retaining means including a groove and a pluraltiy of spring tongues located between said line and said rear edge, said spring tongues being disposed along the Width of the blade and inclined to the plane of the blade and extending into and engaging said groove, said retaining means holding said blade to enable it to rock about a line parallel to said line of support, the spring tongues normally cooperating with the groove to prevent forward withdrawal of the blade from the holder but being disengageable from the groove by rocking the blade when the blade has been lifted off the roll.

9. A doctor according to claim 8, including a pressure plate disposed above the blade and inclined at an angle thereto, means for fastening said pressure plate to said holder, said pressure plate extending forwardly from the holder into engagement with the blade along a line thereof parallel to said edges and between said line of support and the forward edge of the blade.

10. A doctor for a roll of a papermaking or like machine comprising a blade elongated in the direction parallel to the axis of the roll and having a forward edge adapted to engage the roll and a rear edge remote from the roll, said blade having a groove in its upper surface near its rear edge, a blade holder engaging the bottom of the rear of the blade and supporting the same, a pressure plate disposed above the blade and inclined at an angle thereto, means for fastening the pressure plate to the holder with the pressure plate extending forwardly b from the holder and engaging and bearing against the upper surface of the blade along a line thereof located forwardly of the holder, means fastened to the holder including a plurality of downwardly bent spring tongues disposed along the width of the blade and engaging the groove in the blade for normally preventing forward withdrawal of the blade from the holder but enabling a rocking of the blade when the blade has been lifted off the roll for enabling the blade to be disengaged from the holder.

11. A doctor for a roll of a papermaking or like machine, comprising a' doctor blade elongated in a direction parallel to the axis of the roll and having a forward edge adapted to engage the roll and a rear edge remote from the roll, and an elongated holder in engagement with and supporting the rear edge of the blade and having a longitudinal groove beneath the rear end of the blade, the

blade having spaced downwardly bent spring tongues at its rear edge which extend into and engage in said longitudinal groove, a pressure plate disposed above the blade, projecting forwardly from the holder, having its rear edge retained in the holder and bearing against the upper surface of the blade throughout substantially the whole of its length at a region of said upper surface intermediate the front and rear edges of the blade, the spring tongues normally cooperating with the groove to prevent forward withdrawal of the blade from the holder but being disengageable from the groove by rocking the blade about a longitudinal axis thereof when the blade has been lifted off the roll.

12. A doctor according to claim 11, wherein said blade has a plurality of pairs of cutaway portions spaced at intervals along the rear edge of the blade, each of said tonguees being located between a pair of cutaway portions.

References Cited in the file of this patent UNITED STATES PATENTS 2,498,213 Ljungquist Feb. 21, 1950

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